WASHINGTON — The United States plans to send an additional 1,000 troops to Poland to help enhance that country’s ability to defend itself amid fears of Russian aggression in Eastern Europe, a U.S. official said Tuesday.

There are about 4,500 American troops in Poland now on a rotational basis, according to the official, and the additional 1,000 servicemembers will be sent to “enhance mutual interoperability” between the two militaries.

President Donald Trump is expected to make an announcement about the additional troops Wednesday at the White House alongside Polish President Andrzej Duda as part of their discussions on the U.S.-Polish defense relationship.

“We believe it’s going to significantly enhance our military-to-military relationship but also enhance the defense and deterrence posture in Europe… and our commitment to NATO,” a senior White House official said Tuesday during a conference call with reporters about Trump’s announcement regarding the U.S. and Polish militaries.

The plan for the added rotational troops is to integrate them into existing Polish military operations, according to the U.S. official, who spoke on the condition of anonymity. The U.S. servicemembers will not be combat troops. The additional troops in Poland “would potentially focus on providing additional defense and deterrence capabilities in Poland including training, advisers, ISR [intelligence, surveillance and reconnaissance] and sustainment support,” the official said.

When Crimea was seized by Russia from Ukraine in early 2014, Poland began raising alarms about its own security concerns against Russia. Since April 2014, the United States has been sending a rotational brigade to Europe as part of the U.S. Atlantic Resolve mission, where American troops participate in training exercises with allies as well as to serve as a deterrence against Russian aggression in Eastern Europe.

There are also rotational U.S. troops in Poland as part of America’s participation in NATO’s Enhanced Force Presence mission.

kenney.caitlin@stripes.com@caitlinmkenney