The Russian government is likely to "test the mettle" of President-elect Barack Obama and his administration by taking a tougher stance against U.S. missile defenses, a senior State Department official said Wednesday.

John Rood, the department's top arms control official, told reporters he believes the Russians are waiting to size up the Obama administration before Moscow advances its position on disputed arms issues.

In discussing the state of Russian opposition to U.S. missile defense bases in Poland and the Czech Republic, Rood said it appears that Moscow has "paused" in anticipation of a new national security approach in Washington.

"My assessment is that the Russians intend to test the mettle of the new administration and the new president," he said. "The future will show how the new administration chooses to answer that challenge."

Asked to elaborate, he said, "I think missile defense and other subjects will be among those that the Russians intend to determine what the new administration's posture will be." He said he reached this conclusion on the basis of an impression gained during talks in Moscow on Monday rather than from explicit Russian statements.

He also said the Russians have been less flexible lately in talks on missile defense. In particular he cited their stance on U.S. proposals to give the Russians more assurance that a missile interceptor site in Poland and a missile-tracking radar in the Czech Republic would pose no security threat to Russia.

The U.S., with the support of the Polish and Czech governments, has proposed that Russian officials be given regular access to the interceptor and radar sites and that they be allowed to monitor activity at both sites through undisclosed technical means. Rood did not elaborate on the details in dispute.

"I don't want to spell out all the details because I think this is a high-priority dialogue for us in the United States, and I don't think that putting all the details out will facilitate a resolution to it," he said.

Rood led a U.S. government delegation in talks with senior Russian officials on a range of subjects, including efforts by both governments to negotiate a treaty to replace the 1991 START nuclear arms deal, which expires in December 2009. Rood said the talks were useful but did not achieve any breakthroughs.

In Moscow on Tuesday, Russian news agencies quoted Foreign Minister Sergey Lavrov as saying Moscow hopes the Obama administration will agree that the weapons limitations under START "should be preserved and strengthened, rather than weakened."

Rood said the Russians want to expand the scope of a follow-on to the START treaty to include limitations on non-nuclear strategic weapons such as long-range conventional bombers and possibly submarines. The Bush administration has resisted that, saying the restrictions should be on nuclear warheads only.

Rood said he consulted with members of Obama's transition team before traveling to Moscow and will brief them on the substance of the talks. And he said he expects additional talks with the Russians on these subjects before President George W. Bush leaves office Jan. 20.

Brooke Anderson, the Obama transition office's chief spokesperson on national security affairs, declined to comment on Rood's remark about the Russians likely seeking to test the new president.

The missile defense issue has been one of the most divisive over the past few years. The Bush administration has argued that extending its U.S.-based defense system to Europe is important in defending Europe and the United States from a possible long-range missile strike from Iran, while the Russians dispute the immediacy of an Iranian threat and worry about U.S. military expansion near Russian borders.

On Nov. 5, the day after Obama's election, President Dmitry Medvedev warned that Russia would move short-range missiles to NATO's borders to "neutralize" any U.S. missile defense system in Eastern Europe if necessary.

Medvedev has since backed off slightly. He stressed on Nov. 15 that Russia would not act unless the United States took the first step and expressed hope that the new U.S. administration will be open to negotiations.

Obama has not been explicit, at least in public, about whether he would proceed with the missile defense plan in Poland and the Czech Republic. More broadly he has said he supports missile defense but wants to ensure that it is proven to be a reliable system that does not detract from other security priorities.