The United States is continuing its commitment for peace and stability in Eastern Europe, in light of the crisis in Ukraine, a senior Pentagon official said on Monday.

The commitment to collective security in the region will be realized through a series of actions designed to reassure NATO allies and U.S. partners, said Derek Chollet, assistant secretary of defense for international security affairs.

During a conference at the American Forces Press Service, Chollet noted that increased air, land and sea deployments in Eastern Europe are a tangible demonstration of U.S. solid and enduring commitment to collective security and the NATO alliance.

U.S. ships have conducted operations to improve interoperability, increase readiness, and enhance professional relationships, Chollet said.The Ticonderoga-class guided-missile cruiser USS Vella Gulf has been in the Black Sea since May 23. The USS Donald Cook was there in April, followed by the USS Taylor through mid-May.

In April, about 600 paratroopers from the 173rd Infantry Brigade Combat Team deployed for training rotations in Estonia, Latvia, Lithuania and Poland, scheduled to take place for the next few months and beyond.

These are in addition to previously scheduled multinational land force military exercises in the region, defense officials said.

"Americans have served side by side with their European counterparts for many years," Chollet said. "These additional rotations enhance our close relationships and improve our interoperability."

The United States also agreed to fly air-to-air refueling missions to support NATO early warning aircraft flights over Eastern Europe. Endi