As the Obama administration sends signals that it intends to give up missile defense in Europe as part of a security deal with Russia, Secretary of State Hillary Clinton on Tuesday sought to reassure a fellow NATO member -- Poland -- that the U.S. is not abandoning its Eastern Europe ally.

"As members of NATO, we take seriously our alliance commitments and I'm very confident that we will work through any issues that lie ahead -- on any front," Clinton said.

Missile defense is the primary issue between Washington and Warsaw. Poland wants the U.S. to honor its agreement to build a missile defense base in its country.

Poland's president has said that scrapping the project to improve ties with Russia would be an unfriendly gesture toward Poland.

Russia says missile defense in Europe is unnecessary and provocative. Moscow even has threatened to deploy short-range missiles in its westernmost region, bordering Poland, if the U.S. goes ahead. But the rhetoric has since cooled.

Officially, the administration has not said whether it intends to go ahead with the missile defense sites in Poland and the Czech Republic. It has stuck to the language that Obama used as a presidential candidate -- that missile defense must be proved reliable and cost effective.

Missile defense was a favorite of the Bush administration, but it never has been popular among Democrats. Obama's election was seen widely as signaling a death knell for the proposed European leg of the missile defense system, which would be linked to an existing network of interceptors in Alaska and California and radars elsewhere. Scaling back missile defense ambitions also could produce some of the big savings Obama seeks in a period of tight budgets.

In Brussels on Sunday, Polish Foreign Minister Radoslaw Sikorski told Rep. Ellen Tauscher, D-Calif., that Poland took significant political risk signing a pact in August with the U.S. approving a missile defense system in the country.

"Russian generals, and even the Russian president, still continues to threaten us with the deployment of medium-range missiles in our immediate vicinity," he said. "So we signed with the previous administration. We patiently wait for the decision of the new administration and we hope we don't regret our trust in the United States."

"I don't think you will," said Taucsher, who is widely expected to be nominated as the new under secretary of state for arms control.

Tauscher suggested the U.S. could develop a suite of short-and medium-range missile shields, and thereby "bolt" from the long-range system for which Poland was to be one of three sites.

But NATO's supreme commander for Europe who spoke to reporters after Senate testimony, seemed to disagree.

"The third site implementation is given based upon a threat of assessment," said Gen. Bantz Craddock. "I think that stands. Until that changes, I think the impact on U.S. national security are evident, so I will let that stand."

FOX News' James Rosen and The Associated Press contributed to this report.