The Pentagon will more than double the number of fighter jets it is sending to a Nato air policing mission in the Baltics as part of Washington’s response to the Ukraine crisis, officials have said.

The development came after the US Defence Secretary, Chuck Hagel, announced plans to bolster the decade-old mission, which patrols skies over Estonia, Latvia and Lithuania.

Officials said the Pentagon would send six additional F-15 jets and one KC-135 refuelling aircraft to “augment” the mission this week. The US already provides four F-15 jets to the mission.

The planes, reportedly based at RAF Lakenheath in the UK, will fly to the Siauliai Air Base in Lithuania.

“This action comes at the request of our Baltic allies and further demonstrates our commitment to Nato security,” a Pentagon official said. The Pentagon is now said to be “consulting” with Poland on a separate mission.

“This is a time for wise, steady and firm leadership,” Mr Hagel told a Senate panel. “It is a time for all of us to stand with the Ukrainian people in support of their territorial integrity and their sovereignty. We are doing that.”