Senior U.S. and Russian defense officials begin nuclear-arms reduction talks in Washington Tuesday. Despite the recent improvement in relations between the two countries there are many issues to be resolved.

Just three months ago things seemed as if they could not have been rosier. In the aftermath of the September 11 attacks on the United States, Russian President Vladimir Putin had given his complete support to the United States in its fight against terrorism.

In addition, he and President Bush were building a personal relationship that appeared to emphasize the dramatic improvement in ties between their two countries.

But in recent weeks there have been signs of renewed tensions. Moscow expressed its displeasure when Washington unilaterally abandoned the Anti-Ballistic Missile Treaty.

Then the Bush administration voiced its concern about media freedom in Russia, after the only national network outside Kremlin control lost a key court battle to stay open.

And, in the latest incident, Russia charged American diplomats with violating their diplomatic status by taking part in a protest in Vladivostok in support of a Russian journalist convicted of treason. A charge the U.S. rejected.

The talk last autumn of a permanently changed U.S.-Russian relationship now seems to have been overly optimistic. Yevgeny Volk, director of the Heritage Foundation in Moscow, says no one should be surprised. "I think it was some kind of myopic euphoria," he said. "There was a sense of [a] common enemy, common threat and challenges after (the) September 11 tragedy. Now, America emerged as a stronger partner in Russian-American relations and many people in Russia, including the political establishment, do not like American leadership in world affairs."

In the area of nuclear reduction, both Mr. Bush and Mr. Putin have promised to slash their strategic nuclear arsenals by two-thirds during the next decade. But there are large differences over how to go about it.

Russian officials are complaining of U.S. plans to store a number of nuclear warheads instead of destroying them as part of a massive arms reduction.

But analysts here also point out that if it is premature to talk about a new partnership between America and Russia, there is also no need to be too pessimistic.

Independent journalist Masha Lippman maintains that the U.S.-Russian relationship is still strong, chiefly, she says, because of the way Vladimir Putin responded to the September 11 attacks on the United States. "He saw a chance for Russia to join the new alliance with the United States and the rest of the Western world, because I think he clearly realizes that without this integration Russia does not have a chance to develop economically," she said.

The United States and Russia find themselves confronting a new series of obstacles to closer relations.

But as one analyst put it, events since September 11 have demonstrated one thing well. If the United States and Russia are at odds over a number of issues, they at least have proven they can put those differences aside and work together in times of crisis.