Russia may not have abandoned the belief, cited last year by Congressional Research Service analyst Kenneth Katzman, that it needs to offer incentives so Iran won't spread its radical ideology in the Muslim states on its periphery. There are also suspicions of a Moscow-Tehran alliance aimed at preventing U.S. dominance in the Middle East and at giving Russia a strong ally in the Muslim world.
The cooperation is a source of growing alarm to Israel, whose security the United States is committed to protecting. Concerns about Russia's technical help to Iran have been raised by Israeli officials and the pro-Israel lobby in Washington.
Officials say Bush will make the case to Putin that a nuclear-armed Iran could threaten not just the United States and its allies, but also Russia.
"The president, with Putin, will be very clear that there's a common threat here: a dangerous regime with weapons of mass destruction that is a leading state sponsor of terrorism," a White House official said.
The White House is not ruling out a number of possible sanctions if persuasion fails. Analysts say the possibilities include refusing to forgive Russian debts and not using Russian-enriched uranium to power U.S. spacecraft. The United States also might refuse to participate in a new, potentially lucrative Russian plan to store spent nuclear fuel from overseas on its soil, suggested Marvin Feuer of the American Israel Public Affairs Committee.
Also, the United States could hold up Russian entry into the World Trade Organization, a key Putin goal.
But having so recently secured Russia as an ally in his war on terrorism and as a partner with the NATO alliance, Bush would doubtless be reluctant to turn back the clock in U.S.-Russian relations.
"Many of the things you might threaten to block are things that could aid in the further transformation of Russia - the WTO, for example," Fuerth said.