The Euphrates is a real source of conflict between Ankara and Damascus, but no-one in Cairo believes that this was the purpose of the letter. It is Turkey's new military relationship with Israel that was being rammed home to the Arabs, an accord which not only allows Israeli aircraft to fly from Turkish airbases but - so the Arabs have discovered in the past 24 hours - will permit Israeli gunboats to put into Turkish ports within the next week and commence joint naval manoeuvres in the Mediterranean. Understanding all too well the threat this presents to Syria, President Mubarak of Egypt has personally objected to the new Turkish-Israeli alliance. Mr Gonensay's letter was telling him to shut up.
For, at the very moment when the Israeli elections have killed off the "peace process" - at the hour when the Arabs feel most betrayed by the promises of land-for-peace that they received from Israel and America over the past five years - a new strategic partnership is emerging to take the place of the long-promised peace accords; an alliance of Turkey, the US, Israel and Jordan, designed to form a military front against - and to isolate - the West's supposed enemies in the Middle East. In essence, it is a shadowy version of the Baghdad pact, the British-sponsored alliance of Turkey, Iraq, Iran and Pakistan that was set up in 1955 to counter fears of Soviet expansion in south-west Asia. The new pact, however, is to protect Israeli and American interests against those Muslim states that oppose their policies in the Middle East.
The setting-up of this new alliance was conceived and carried out with extraordinary speed. In February of this year, the Turkish army's deputy chief of staff paid a secret visit to Israel, during which he and Shimon Peres agreed that their military aircraft could fly for "training purposes" in each other's airspace. At almost the same time, King Hussein of Jordan, who has never forgotten his family's Hashemite claim to Iraq, was encouraged to propose a federation between Amman and Baghdad that would, in effect, place a Saddam-free Iraq under the control of the Jordanian monarchy. Already locked into a full peace treaty with Israel - King Hussein signed the agreement in the days when both the Americans and the Israelis had promised a just peace for Palestinians and Syrians - Jordan was persuaded that US jets should be given a "temporary" base in his country, near the Iraqi border to defend Amman if Saddam Hussein decided to revenge himself upon the King.
With American jets already flying out of airfields in Saudi Arabia, Kuwait, the United Arab Emirates and Oman - a privilege they gained from the 1991 Gulf war - the US Air Force had thus established itself several hundred miles east of Israel just as the Israelis gained the right to fly across Turkey to the very borders of northern Syria and Iran. No wonder President Rafsanjani of Iran told the Turkish President Suleyman Demirel last month that the Israelis could now fly out of Turkey to bomb Tehran. No wonder Syria suddenly concluded that it had a potential enemy on two fronts - the Israeli army to the south on Golan and the Turkish army and Israeli air force just across its northern border.
And at the very moment when Syria discovered its new military predicament, it found itself under physical as well as political attack. A series of small bombs exploded in Syrian cities - no one was hurt and the bombs were more a warning than an assault - but the Syrians noted that the former Turkish prime minister, Tansu Ciller, would not disclose the purpose of a $6m payment from a special "discretionary operations fund", because this might "damage relations" with neighbouring states. Did the Turkish government plant the bombs? And did it do so because of Syria's support for the Kurdish PKK separatist guerrillas fighting the Turkish army? And, if so, did the Turks have the tacit permission of security authorities in Washington?
Of course, no one should be romantic about Syria. It is a police state. Its prisons still hold many men categorised as political prisoners by Amnesty International. The consistent use of police torture in Syria has been widely condemned. Hamas does maintain an office in Damascus, and Syria certainly supports the Hizbollah struggle against Israeli occupation in southern Lebanon.
President Assad is now being reviled as the man who was offered back the whole of the occupied Golan Heights in return for peace, but who then turned down the deal. That this is untrue has not changed the accusations that President Assad has been "the chief obstacle to peace". What he was offered was most of the Golan Heights but with no promise of the departure of Israeli settlers and a demand from Israel - in return for the evacuation of occupied territory - that Syria must substantially reduce her military forces. One Syrian estimate suggested that more than 30 per cent of Syrian armour would have to be scrapped to comply with such a demand and that troop withdrawal conditions laid down by Israel would mean that not a single soldier could remain in the capital of Damascus, which lies only a few miles north of the current ceasefire lines.
President Assad, like all the other Arab leaders who sent representatives to the Madrid summit in 1991, was promised by the US that any peace agreement with Israel would be on the basis of UN security council resolutions 242, 338 and 425 - of land for peace. The Syrian leader possesses a confidential letter to this effect from then Secretary of State James Baker. US negotiators - at times even the Israelis - have acknowledged that President Assad stuck rigidly to this formula. Those who trusted the Americans and Israeli promises that they would get their land if they made peace first - the hapless Mr Arafat and his supporters - have ended up with a peace agreement which Israel, under its new government, says it has no intention of honouring. Mr Netanyahu has been quite specific. There will be no Palestinian capital in any part of Jerusalem, no Palestinian state, no evacuation of settlements, no withdrawal from the Golan Heights. In other words, the Oslo agreement cannot proceed to the "final stage" talks, which contain the most crucial issues of the "peace" - Jerusalem and settlements - while the very basis of the Syrian negotiations, an Israeli withdrawal from Golan, has been destroyed.
All this is clear to the Arab leaders meeting in Cairo tomorrow. Yet they find that the Americans who had so earnestly told them to trust Israel's good intentions are now welcoming - in the words of State Department spokesman Nicholas Burns - Mr Netanyahu's offer of talks with Syria "without conditions". But Mr Netanyahu has already set the condition for peace talks with Syria: no return of the Golan Heights. And all the while, it is Syria that is being vilified as the peace-destroyer, the nation that undermined the chances of a lasting accord in the Middle East. Put very bluntly, Syria is being lined up for attack.
In the Gulf, meanwhile, the ever-compliant emirs and monarchs are desperately trying to assess their own future. Those who had opened ties with Israel - Oman and Qatar - may be able to escape further contact, but just as the Levant is being told to regard Syria as the Prince of Darkness, so the Gulf states are being warned that only the West can protect them from the terroristic, revolutionary expansionism of Iran.
A real territorial dispute between the Emirates and Iran has been augmented by repeated assertions from Washington and London that Iran lies behind the home-grown Shiite insurrection in Bahrain. Iran is in any case already on Washington's hit list, under US - though not European - sanctions, ever since President Clinton denounced the regime as a "terrorist" state at a Jewish meeting in New York last year. Iran has joined the other "enemies of the West" - Libya, Sudan and Iraq. And now, it seems, Syria may well follow.
Whenever Palestinians resort to violence because their "peace" has been betrayed, Syria and Iran or Libya or Sudan or even Iraq will be blamed. Those faithful to the Western cause - Jordan, Israel and now Turkey - will support this notion; already, Jordan has discovered Syrian "terrorists" on its border.
Then what of Egypt, the first Arab nation to make peace with Israel? For she, too, is isolated in the Arab world - not by her enemies, but by her Western friends. To the west, Libya is in quarantine because of its alleged role in the Lockerbie bombing. To the south, Sudan is also under UN sanctions for supporting "terrorists". To the east, Yasser Arafat's Gaza enclave is itself sealed off by Israel for fear of "terrorism". Egypt's role as a peacemaker has been marginalised; the promises President Mubarak urged Arafat to accept have been broken. Jordan, the Arab state that showed the warmest regard for Saddam after his invasion of Kuwait, is now to be the front line against Iraq. The great Middle East military ally of Israel is to be Turkey, not Egypt.
President Mubarak is deeply concerned at Israel's nuclear potential, at the expressions of unrest within his own military forces, at America's threats of military strikes against Libya. Cairo, it seems, is to be turned into a political backwater, a conference centre for obedient Arab states. President Mubarak was appalled when he heard of the new Israeli-Turkish alliance; it made him even more anxious to help President Assad now that another pillar of the Arab world is under assault. Which is why it is for Syria that tomorrow's summit is primarily being held. President Mubarak and President Assad are likely to stand together now as never before, for they both fear that dark days lie ahead. A military strike into Syria by Turkey or Israel, another Israeli assault into Lebanon after further conflict between Israeli occupation troops and the Hizbollah, perhaps even a military strike at Iran itself, a Palestinian-Israeli war in the West Bank: all are now possible.
President Mubarak has said he will not allow Syria to be attacked, a dangerous promise for a man whose country's economy has been bankrolled by the US in return for Egypt's peace with Israel. But every Arab state friendly to the West will feel the earth tremors from any new military adventures in the Middle East. Few Arabs would dispute the gloomy prediction made by one prominent Middle East figure this week. "There could have been four wonderful years..." he said after the Israeli elections. "But four very difficult years - very difficult - are in store for us." The speaker was Shimon Peres.