More funding expected for European defense.

The Pentagon is ramping up its investment in the European Reassurance Initiative, which is designed to deter Russia and support nervous NATO allies concerned about Moscow's intervention in Ukraine and elsewhere.

The Defense Department requested $3.4 billion in fiscal year 2017 to fund a range of activities. The money would support additional U.S. force rotations in Europe, expanded training and exercises with U.S. allies, more prepositioned warfighting gear and infrastructure improvements to support it, according to Pentagon officials.

"When combined with U.S. forces already in and assigned to Europe... all of this together by the end of 2017 will let us rapidly form a highly capable combined arms ground force that can respond across that theater if necessary," Secretary of Defense Ash Carter said during a recent budget discussion hosted by the Economic Club of Washington, D.C.

The funding would quadruple the amount appropriated for the reassurance initiative in fiscal year 2016, which was approximately $800 million.

The Pentagon sees growing geopolitical competition between the United States and Russia. Concerns about Moscow's intentions and capabilities is a top challenge "now driving the focus of the Defense Department's planning and budgeting," Carter said.

"We're taking a strong and...