LEADING ARTICLE : Bill and Boris - powerful men

The summit tomorrow between the leaders of Russia and the United States follows on a common act of celebration, but its atmosphere of tension permits no false rejoicing. Fifty years after Stalin and Truman found their gigantic forces face to face on the Elbe, the relationship between these two leviathans continues to govern the overall security of Europe. We can only watch anxiously how President Clinton and President Yeltsin work to resolve the dramas that can still shake the equilibrium between them.

First we should understand the Russian mood. Half a century past, Russia stood bruisedly victorious, its lifeblood and treasure expended in what Soviet historians called the Great Patriotic War. The title alone spoke of the mystical nationalism that underpinned Stalin's reach to the high watermark of several centuries of Russian expansion. The tide has rolled back with alarming speed since 1989. The Soviet Union is no more: its certainties dismantled, its economic security in tatters, its politics volatile, its subject peoples now grouped by Russian diplomats under the curious heading of the Near Abroad. The Soviet frontiers of 1939 have been replaced by the boundaries of a free Ukraine and Belarus, hundreds of miles nearer Moscow. No Russian leader could fail to be intimidated by such a readjustment. Only the possession of nuclear weapons and a large conventional army confers on Russia its superpower status - and the botched campaign in Chechnya testifies to the army's deficiency.

Thus Mr Clinton confronts a Russia in truculent frame of mind. At the top of Mr Yeltsin's agenda is the need to prevent the expansion of Nato to the east. This stance presents policymakers with a dilemma. Do they press ahead to create a new security system or do they linger, fearful of Russian ire or internal Russian upheaval? "No vetoes and no surprises" remains the Western catchphrase. For the moment it is hard to think of a better one.

Intertwined with this question is the future of Russia's free market reforms and its fragile democracy. Mr Yeltsin can seem pretty much an autocrat when he wants, but like Mr Clinton he is scheduled eventually to face the verdict of the electorate. Conventional wisdom states that Mr Yeltsin is the least worst thing on offer in Moscow, so he should be buttressed by aid and not made to lose face. But just as Mr Yeltsin must defer to Russian nationalists, so Mr Clinton needs to take account of US conservatives who control the Congress. The administration needs to fight on Capitol Hill for every dollar in aid and every tiny arms reduction.

These double constraints do not augur well for either Russian or American aspirations at the summit. But smaller countries should resist the temptation to quiet satisfaction at their bind. It would be better if President Yeltsin were not locked into an ill-judged venture to sell nuclear reactors to Iran by a fear of looking weak. It would be better for the former Yugoslavia if both parties were not entangled by pro-Serb orthodoxy in Moscow and a selectively outraged pro-Bosnian camp in Washington. If the Balkans go up in flames, it will be due in no small part to the cynical posturing of both Russian and American politicians.

Five decades ago yesterday, Churchill sent a message of congratulation to Moscow and then turned to warn the British people "not to fall back into the rut of inertia, the confusion of aim and the craven fear of being great". That would not be a bad warning to deliver to tomorrow's summiteers.