The United States is to withdraw some 7000 combat troops from Europe, as part of measures to reduce military spending.
Defence Secretary Leon Panetta said the troops will be replaced with rotational units to ensure a continued strong presence in the region.
Some 80,000 US military personnel are currently based in Europe. The US is redirecting its attention to the Asia-Pacific region.
In an interview with the American Forces Press Service, Mr Panetta said America's security commitments to Europe and to NATO were ''unwavering''.
Rotating troops in and out of Europe, rather than having them stationed there, would mean a considerable reduction in cost.
The BBC reports Mr Panetta did not give a timescale for the withdrawals.
The United States currently has four combat brigades stationed in Europe - three in Germany and the fourth in Italy.
The troops have regularly been deployed from Europe to combat duties in Iraq or Afghanistan.