Speaking after a meeting in Moscow between President Boris Yeltsin and the US Secretary of State, Warren Christopher, Russia's Foreign Minister, Yevgeny Primakov, said: "Russia will never accept Nato enlargement, not because it has any right of veto, but because it will not tolerate a worsening geopolitical situation and will stand by its interests."
Russia's leadership regards Nato's planned expansion as a challenge to Russian security that could throw Europe back into a second "Ice Age" of East-West confrontation. But Mr Christopher, speaking in Prague last Wednesday to 12 central- and eastern-European foreign ministers, reaffirmed that Nato had committed itself to expansion and said the region's new democracies would not be kept waiting forever.
Mr Primakov suggested a compromise might be possible if Nato did not move its "military infrastructure" into potential new member-states such as the Czech Republic, Hungary and Poland. However, both Nato and the three central European states are adamant that Russia cannot dictate the terms of their admission into the alliance.
Nato's Secretary-General, Javier Solana, visited Moscow earlier in the week and urged Russian leaders to recognise that Nato no longer resembled the military alliance that it was in Cold War times. However, the Russians repeated their argument that Nato's expansion would represent an unacceptable extension of Western influence up to Russia's borders.
Despite the clash of views over Nato, Mr Christopher made clear that the US still had faith in Mr Yeltsin's reformist potential and hoped he would emerge victorious from next June's presidential election. He said that President Bill Clinton's policy was "to support the reforms and those who are enthusiastic about reforms and who are carrying out reforms. That has brought him into strong support for President Yeltsin on prior occasions."
Mr Clinton is due to travel to Moscow on 19-20 April for a summit with Mr Yeltsin on nuclear security. The visit is likely to be interpreted as a show of US solidarity with Mr Yeltsin.
Mr Yeltsin faces a strong challenge from the Communist leader, Gennady Zyuganov, whose party sent shock waves across eastern Europe last week by pushing a resolution through the Russian parliament that called for the restoration of the Soviet Union. However, the parliament avoided a clash with Mr Christopher yesterday by ignoring a draft resolution from a Communist deputy that denounced the Secretary of State for criticising last week's vote.
Mr Yeltsin, the chief architect of the Soviet Union's dissolution in 1991, has declared himself firmly opposed to Mr Zyuganov's stated aim of recreating the Soviet state by peaceful means. However, after his talks with Mr Christopher, Mr Yeltsin was playing host to the President of Belarus, Alexander Lukashenko, who advocates the integration of his country with Russia.
"I will propose to Mr Yeltsin the signing of a treaty free of all ambiguities and creating union institutions of a supranational nature," Mr Lukashenko said before leaving Minsk for Moscow. When he visited Moscow last month, he and Mr Yeltsin signed documents on integration that have yet to be made public.
The Russian authorities have not been entirely enthusiastic about Mr Lukashenko's proposals in the past, partly because they would require substantial Russian economic support for Belarus.