Iran is funnelling money into Iraq to influence the outcome of its elections, the US Defence Secretary James Mattis said, calling it part of a broader pattern of destabilising Iranian actions across the Middle East.
"We have worrisome evidence that Iran is trying to influence — using money — the Iraqi elections," Mr Mattis told reporters flying with him to Washington from Bahrain, where he discussed Iran and other issues with senior government officials.
"That money is being used to sway candidates, to sway votes — not an insignificant amount of money, we believe, and it's highly unhelpful," he said.
"We know that they are doing what they can to impact the elections, and we don't like it."
Mr Mattis mentioned no amounts, but his comments on Thursday came as the US National Security Adviser, HR McMaster, said Iran had given more than $16 billion (Dh58.7bn) to the Assad regime in Syria and to proxies in Syria, Iraq and Yemen.
Iran increased its influence in Iraq by supporting the mainly Shiite militias that were mobilised to fight ISIL after the extremist group seized much of the north and west of the country in 2014. Many figures from the militias are taking part in the general election scheduled for May.
Prime Minister Haider Al Abadi is seeking another term after Iraqi government forces, backed by the militias and the US mliitary, reclaimed the territory seized by ISIL.
Iran's political influence in Iraq has grown since the US invaded to remove president Saddam Hussein in 2003, marking the start of a prolonged period of sectarian division, extremist violence and political strife.
Mr Mattis also criticised Iranian meddling elsewhere in the Middle East. He said Tehran was providing ammunition and explosives to fighters in Syria, and supporting rebels in Yemen.
He said the Bab Al Mandeb strait off the coast of southern Yemen was being used as a "proving ground" for advanced Iranian weaponry, including anti-ship missiles, radars, mines, ballistic missiles and explosive boats.
On the other hand, Iran has stopped conducting provocative and dangerous manoeuvres against US navy ships in the Arabian Gulf, Mr Mattis said.
"It's like an outlier, and I don't know why," he said. "They don't seem to be engaging in the same provocative behaviour" in the Gulf as they were prior to last summer.
Commander William Urban, a spokesman for US Naval Forces Central Command in Bahrain, said earlier on Thursday that there had been no "unsafe and unprofessional" actions by Iranian naval forces in the Gulf since August.