(Reuters) - Iran launched missile attacks on U.S.-led forces in Iraq early on Wednesday, including the al-Asad air base, in retaliation for the U.S. drone strike on an Iranian commander whose killing raised fears of a wider Middle East conflict.

The attacks came hours after U.S. Defense Secretary Mark Esper said the United States should expect retaliation over the U.S. killing of Iranian military commander Qassem Soleimani in a drone strike in Iraq on Friday.

It was the latest strike against an air base that has figured prominently in high-ranking officials' visits.

TRAINING

U.S. troops have trained Iraqi troops at the base, located in Anbar province northwest of Baghdad, as part of Washington's bid to build a force that could mount an offensive against Islamic State militants.

Aside from U.S. and Iraqi forces, the air base has also hosted U.S.-led coalition partners Denmark and the United Kingdom.

BASE HAS HOSTED TRUMP

Over the Christmas holidays in 2018, U.S. President Donald Trump stopped there and made remarks to troops during a surprise visit to Iraq, his first journey to a conflict zone since taking office in January 2017.

During Trump's trip, he defended his decision to withdraw 2,000 troops from Syria. That policy shift sparked concern from allies and spurred James Mattis, his defense secretary at the time, to resign.

THE BASE HAS BEEN ATTACKED BEFORE

In 2015, the base came under regular harassing mortar fire from Islamic State militants.

The same year, the air base was attacked by 25 Islamic State fighters, but the Pentagon said at the time that Iraqi security forces guarding the perimeter killed most of the combatants.

Five rockets landed on the air base last month but did not cause any casualties.

Reports circulated last week that the air base had come under attack. Sources told Reuters, however, that reports of an attack on the base were false.

(Writing by Makini Brice; Editing by Mary Milliken and Peter Cooney)