President Bush’s meeting with Russia’s Vladimir Putin this weekend probably will be their last while Putin is still president. Once again, controlling the threat of nuclear weapons is circling back to American and Russian leaders.

This time, the immediate issue in that minefield is expanding U.S. missile defenses in Eastern Europe. Bush argues that bases in Poland and the Czech Republic serve the defense of many nations, including Russia. Putin suspects the defense is aimed at Russia.

As an inducement, the United States is prepared to promise not to activate the new sites unless Iran proves to be an imminent threat to Europe by test-flying a missile capable of reaching the continent.

“Obviously, we’ve got a lot of work to do to allay suspicions and old fears, but I think we are making pretty good progress along those lines,” Bush said Tuesday.

Bush added in a speech Wednesday in Romonia that he will reiterate to Putin “that the missile defense capabilities we are developing are not designed to defend against Russia just as the new NATO we are building is not designed to defend against Russia.”

“The Cold War is over,” he said. “Russia is not our enemy. We are working toward a new security relationship with Russia whose foundation does not rest on the prospect of mutual annihilation.”

An agreement may emerge, one that partners the United States and Russia again in controlling the pathway of the nuclear age.

A Kremlin spokesman said Tuesday that officials on both sides were working on a document setting out a “strategic framework” for relations beyond their time in office.

“We proceed from the assumption that we will succeed in completing the work and that it will be adopted in some form,” spokesman Dmitry Peskov told The Associated Press in Moscow.

What Bush and Putin decide to do would have only a tangential impact on the worrisome nuclear programs of North Korea and Iran. But their two nations sit atop the world’s most massive nuclear arsenals. Their cooperation, based highly on trust, seems essential.

Under the 1991 Strategic Arms Reduction Treaty, the United States and Russia are limited to no more than 6,000 nuclear warheads each. Both nations are believed to be way below those totals.

In 2002, Bush and Putin agreed on a treaty that sets as a target 1,700 to 2,200 deployed strategic warheads by 2012.

Abandoned by the Bush administration from the outset was the longtime methodical process of negotiating the smallest details of nuclear reductions as well as verification procedures to guard against cheating. And setting a target is something less than a concrete agreement.

In the meantime, the START treaty is due to expire at the end of next year, and Russian and American officials have been unable to chart an agreement for a successor pact.

It is not certain whether Bush and Putin, meeting at the Black Sea resort city of Sochi, will come to terms on either missile defense systems or reductions in strategic arms.

But if their meeting is marked by good will and relations have overcome the bumps that followed Bush’s initial positive impression of Putin, a course toward a solution could be set.

That first meeting, in June 2001, stirred hopes of a positive relationship when Bush said he had looked into Putin’s eyes and “was able to get a sense of his soul.”

Putin steps down as president next month. By all accounts, though, he will remain a driving force in Russian policy after his hand-picked successor, Dmitry Medvedev, takes over.

Bush has met with Putin some 20 times, according to an unofficial White House count, more often than with any other foreign leader except Britain’s Tony Blair. “Both have invested a lot in this relationship, but they haven’t had a big payoff,” said Andrew Kuchins, director of the Russia program at the Center for Strategic and International Studies.

“I think they would like to reverse that trajectory,” Kuchins said in an interview.

The notion that they would make headway on a broad strategic framework, extending the START treaty and on verification measures should not be ruled out, Kuchins said.

“What drives me to be optimistic is that fundamentally we are not a threat to Russia and Russia is not a threat to us,” he said.

Daryl Kimball, executive director of the private Arms Control Association, faults both Bush and Putin for “failure to overcome the rivalry and Cold War attitudes of their predecessors.” He noted in an interview they will leave behind enormous nuclear missile stockpiles.

The next president of each country will have a responsibility to negotiate a new agreement and framework to verifiably slash each nation’s arsenal, Kimball said.

“Failure to replace START would leave behind an atmosphere that will perpetuate Russian concern about U.S. strategic nuclear capabilities and could diminish U.S. capability to chart what Russia is doing,” he said.

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EDITOR’S NOTE _ Barry Schweid has covered arms control and diplomacy for The Associated Press since 1973.