Blinken met Iraqi Prime Minister Mohammed Shia al-Sudani in Baghdad on Friday as part of a last-minute regional tour after Islamist-led Syrian rebels ended a half-century of rule by the Assad clan, a major ally of Iran.

A US official said Blinken told Sudani that Iran was at its weakest in some time and that Iraq had an opportunity to reduce Tehran's influence.

Specifically, Blinken asked Sudani to clamp down on Iranian-backed Iraqi Shiite armed groups, who for years have periodically attacked US forces in Iraq, the official said on condition of anonymity.

Blinken also asked Sudani to help prevent the transfer of Iranian weapons across Iraqi territory to any affiliated groups in Syria, the official said.

Blinken was more circumspect in his public remarks, saying after their meeting in Baghdad that the US was committed to "working for Iraq's sovereignty to make sure that that is strengthened and preserved".

"I think this is a moment as well for Iraq to reinforce its own sovereignty as well as its stability, security and success going forward," he said, without naming Iran.

Iran's clout rose sharply in its fellow Shiite-majority neighbour after the 2003 US-led invasion toppled Tehran's foe Saddam Hussein.

Assad's government in Syria had long been propped up with help from Iran and its powerful ally Hezbollah in Lebanon.

The Tehran-backed group, however, suffered heavy losses in its recent war with Israel, which has also struck Iran-linked targets within Syria.

Assad's other key backer Russia, meanwhile, has been tied up by its invasion of Ukraine.

The US official declined to say how Sudani responded to Blinken's request, other than to say the prime minister expressed hope Iraq could avoid becoming embroiled in a conflict.

Blinken also promised to work with Iraq to prevent a resurgence of the ultra-violent Islamic State group, which established a self-styled caliphate across vast swathes of Iraq and Syria a decade ago before counter-offensives backed both by the United States and Iran.

The Iraqi government has close ties to Iran, and US President Joe Biden's administration has agreed with Baghdad to reduce the remaining US troop presence in the country -- a long-standing demand of Iran-aligned militias there.

The incoming administration of Donald Trump is expected to harden US actions against Iran, even though the president-elect has also voiced a willingness for deal-making.

The Biden administration last month extended again a waiver allowing Iraq to buy electricity from Iran in spite of sanctions.

Lawmakers from Trump's Republican Party lashed out at the move, saying that Biden was permitting a major cash flow to Iran that worked against international efforts to isolate it.