Washington ? The Russian government is likely to “test the mettle” of 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.