There is a simple bit of commercial arithmetic which the Russian Prime Minister, Mr Sergei Stepashin, is asking the Clinton administration this week to add up for him. The sums answer the question: can Russia ever trade its way out of insolvency?

Since the fourfold devaluation of the rouble in August 1998, the ratio of Russia's foreign debts to its gross national product has jumped from 28 per cent (start of 1998) to 111 per cent estimated by the end of this year; 116 per cent is projected for next year.

While devaluation has stimulated increased export volumes, as well as growth of domestic production (substituting for imports), the crash in the dollar value of Russia's income, and hence of its ability to service its dollar debts, is almost unprecedented internationally. A few days ago, the Russian debt negotiator, the Deputy Prime Minister, Mr Mikhail Zadornov, admitted officially what has been obvious to everyone for months, if not years. If Russia is to keep paying its debt bill - ranging from $13 billion to $19 billion annually to 2008 - it will have nothing left in the budget, no matter how high world oil and other commodity prices go and how hard the Kremlin taxes the exporters.

His solution? It was a "fatal mistake", he said, for the Russian governments of President Boris Yeltsin's first term to agree to take over and repay Soviet debts. These amounted to $66 billion at the beginning of this year - about 45 per cent of Russia's external state debt. Mr Zadornov, who was finance minister ahead of last year's crash, has never been so bold before. He is admitting that the choice now facing Mr Stepashin, and whoever succeeds President Yeltsin, is brutal.

Either Russia gets forgiveness of the Soviet debt, plus rescheduling of the debts run up since 1991, or else it will have no chance to revive its economy. The Clinton administration can see the political implications of this quite well. Russia will have parliamentary elections in December, and presidential elections are scheduled for June 2000.

In the short term, Washington is almost certain to finance emergency shipments of wheat into the Moscow region, along the Volga river, and in other population centres, where there are already serious grain shortages. By election time in mid-December, Russian voters will have to be paid, at least in bread, or the Communist Party will annihilate the government's candidates. Washington must also decide which candidate to back next year for president, if Mr Yelt sin goes, as he has promised, and as the constitution requires.

The US Vice President, Mr Al Gore, the Under Secretary of State, Mr Strobe Talbott, and the Treasury Secretary, Mr Lawrence Summers, all backed the removal in May of the man who is still, three months later, the most popular candidate to be president, the prime minister, Mr Yevgeny Primakov.

His policy on debt reflected the precariousness of his political position. To preserve support from Germany - whose banks hold most of the Soviet debt - Mr Primakov swore to keep up repayments, and not to ask for forgiveness.

If he teams up with the Moscow mayor, Mr Yury Luzhkov, and they receive the backing of the Communist Party, they will win the presidency, whoever the opposing candidate may be and however much money the international community funnels into the campaign.

A Primakov-Luzhkov victory will almost certainly mean the abandonment of Soviet debt.

Mr Stepashin needs US support if he is to survive the parliamentary elections and run for the presidency next year. Behind him stands Mr Anatoly Chubais, the former finance minister who dug Russia into the debt hole deeper than any other official. Mr Chubais has been Washington's favourite and he may be still, but he is unpopular with Russian voters and is unelectable.

As his stand-in, Mr Stepashin can promise to maintain Russia's debt repayments, but he cannot avoid reckoning with the "fatal mistake", as Mr Zadornov calls it.

As a professional policeman, not an economist, the prime minister has been explaining in the US this week that short-term aid will not resolve the deeply destabilising effect of another decade without growth. He is seeking Washington's political backing for a stable transition into the post-Yeltsin era. The arithmetic of stability, he will say, adds up to debt forgiveness.