US Defence Secretary Jim Mattis has accused Iran of channelling cash to influence the Iraqi parliamentary elections due in May.
US Defence Secretary Jim Mattis has accused Iran of "mucking around" in Iraq's May parliamentary election, in which Prime Minister Haider al-Abadi is seeking another term.
The ballot will decide Iraq's leader for the next four years, when Baghdad will be faced with rebuilding cities and towns seized from Islamic State, preventing the militants' return and addressing the sectarian and economic divisions that fuelled the conflict.
Among Abadi's challengers are former Prime Minister Nuri al-Maliki and Hadi al-Amiri, a former transportation minister - both of whom are among Iran's closest allies in neighbouring Iraq.
Mattis stopped short of detailing whom Iran sought to influence but said it was doing so by channelling cash into Iraqi politics.
"We have worrisome evidence that Iran is trying to influence - using money - the Iraqi elections. That money is being used to sway candidates, to sway votes," Mattis told reporters as he flew back to Washington after a trip to the Middle East and Afghanistan.
"It's not an insignificant amount of money, we believe. And we think it's highly unhelpful."
There was no immediate comment from Iran, which has in the past denied interfering in Iraq.
Mattis compared Iran's actions to those of Russia, which the US intelligence community has concluded attempted to influence the 2016 US presidential election in favour of Donald Trump.
He declined to say whether the Iranian effort had been successful or whether Iran sought to undermine Abadi.
Mattis said his trip to Afghanistan and the Middle East reinforced his concerns about Iran's activities in the region, from stoking violence in Syria to aiding insurgents in western Afghanistan.
The United States also accuses Iran of escalating the civil war in Yemen and threatening to turn it into a broader regional conflict by supplying advanced weaponry, including missiles, to Houthi rebels who have fired at targets in Saudi Arabia.