Leading article: No alternative to diplomacy in Syria

From the beginning, one of the greatest fears about the Syrian crisis has been that the civil war inside the country would spread beyond Syria, along the familiar political and religious faultlines of the Middle East. This week's overspill of violence into Turkey and Lebanon is a grim sign that this may be starting to happen – just as the conflict itself seems further from resolution than ever.

The best, if slender, hope of a ceasefire still lies with the six-point plan brokered by the Arab League's envoy, Kofi Annan, that was supposed to have come into effect yesterday. In reality, the slaughter of its own citizens by the regime in Damascus appears to be continuing unabated. Once again, President Assad has prevaricated and lied to buy more time for his army, with its vastly superior firepower, to impose a solution by brute force. This reflects a basic truth: Mr Assad is fighting for his life. He knows that any negotiated deal would merely hasten the end. Thus if the Annan plan fails, no other formula is likely to bring a truce. And in the absence of a truce, every indication is that the crisis will worsen.

The Arab world is divided, while Turkey may simply run out of patience at Syrian incursions into its territory. In the West, calls are intensifying for large-scale military assistance to the opposition. But such a step would simply increase not only the carnage within Syria (and with no guarantee the Assad regime would be toppled), but also the likelihood that other countries in the region are drawn directly into the conflict.

The only alternative is massive diplomatic pressure, however unpromising the chances of success. The Annan plan at least has the backing of China and Russia, who previously used their veto powers to block tough action against Damascus by the UN Security Council. Russia, the regime's most important international protector, is now urging Mr Assad to be "more active" in implementing the ceasefire proposals, but does not seem to have withdrawn its support. Until Moscow does so, the Syrian crisis is destined only to deepen, imperilling the stability of the entire Middle East.