WARSAW (Reuters) - The first main U.S. forces are expected to arrive in Poland on Saturday, defence sources told Reuters on Friday, in order to reinforce NATO's eastern flank as the West and Russia wrangle over Russia's military presence near the Ukrainian border.

       The sources, who requested anonymity due to the sensitive nature of the troops' arrival, said the plans could change depending on security and logistics.

       President Joe Biden's administration on Wednesday announced the deployment of nearly 3,000 American troops to eastern Europe in the coming days amid a standoff with Russia over Ukraine.

       Around 1,700 soldiers from the 82nd Airborne Division based at Fort Bragg, North Carolina, are meant to come to Poland, Poland's Defence Minister Mariusz Blaszczak and the Pentagon said on Wednesday, but only on a temporary basis.

       A small group of soldiers from the U.S. Air Force's 435th Air Ground Operations Wing, which is headquartered at Ramstein Air Base in Germany, arrived on Thursday to prepare for the arrival of the troops and military equipment.

       More flights with equipment landed on Friday at Rzeszow-Jasionka airport in Southern Poland.

       The U.S. military already has about 4,500 troops in Poland in both a NATO and a bilateral capacity, mostly stationed in the west of the country on a rotational basis.

       (Reporting by Joanna Plucinska; additional reporting by Phil Stewart in Washington; editing by Jonathan Oatis)