WASHINGTON, May 14 (UPI) -- A State Department official told Congress on Thursday that NATO remains a critical deterrent to Russian aggression, and he reaffirmed U.S. support for the Baltic states.

That reassurance comes as the war in Iran has resulted in delayed U.S. weapons shipments to Europe and the Pentagon canceling a planned deployment of 4,000 troops to Poland.

"The U.S. remains firmly committed to standing with our Baltic allies," Christopher Smith, deputy assistant secretary in the Bureau of European and Eurasian Affairs, told the House Foreign Affairs Committee's Europe Subcommittee. "These allies are leading the charge in NATO."

Smith's testified amid growing concern among European allies about Washington's military commitments overseas.

President Donald Trump has pushed NATO members to take greater responsibility for their own defense in recent months. And the administration announced plans to withdraw thousands of U.S. troops from Germany, while the Baltic states, wary of Russia as the war in Ukraine enters its fifth year, have sharply increased defense spending and sought reassurances of continued American support.