"Four rockets fell in the vicinity" of Ain al-Assad base in Anbar province, an Iraqi security source said.

Another security official said an attack occured with "a drone and three rockets" that fell close to the base perimeter.

A US official said initial reports indicated that projectiles landed outside the base without causing injuries or damage to the base.

All sources spoke on condition of anonymity because they are not authorised to speak to the media.

There was no immediate claim of responsibility.

Iran-backed armed groups in Iraq have largely halted similar attacks on US-backed troops in recent months.

Thursday's attack came after a security meeting this week between Iraqi and US officials in Washington on the future of the international anti-jihadist coalition in Iraq. Iran-backed groups have demanded a withdrawal.

The US Defense Department said Wednesday that "the delegations reached an understanding on the concept for a new phase of the bilateral security relationship."

This would include "cooperation through liaison officers, training, and traditional security cooperation programs."

On July 16, two drones were launched against Ain al-Assad base, with one exploding inside without causing injuries or damage. A senior security official in Baghdad said he believed the attack was meant to "embarrass" the Iraqi government before the security meeting.

For more than three months, as regional tensions soared over the Israel-Hamas war in Gaza, US troops were targeted more than 175 times in the Middle East, mainly in Iraq and Syria.

The Islamic Resistance of Iraq, a loose alliance of Iran-backed groups, claimed the majority of the attacks, saying they were in solidarity with Gaza Palestinians.

In January, a drone strike blamed on those groups killed three US soldiers in a base in Jordan. In retaliation, US forces launched dozens of strikes against Tehran-backed fighters.

Since then, attacks against US troops have largely halted.

Baghdad has sought to defuse tensions, engaging in talks with Washington on the future of the US-led coalition's mission in Iraq.

The US military has some 2,500 troops deployed in Iraq and 900 in Syria with the international coalition.

The coalition was deployed to Iraq at the government's request in 2014 to help combat Islamic State, which had taken over vast swathes of Iraq and neighbouring Syria.