U.S. Secretary of State Mike Pompeo made an unscheduled visit to Baghdad after canceling a planned meeting with Chancellor Angela Merkel in Germany.
On the way to Baghdad on Tuesday, Pompeo told reporters he would meet with Iraq's president and prime minister to show them what he said is USA support for "a sovereign, independent" Iraq, free from the influence of neighbouring Iran. Pompeo said he made the trip because Iranian forces are "escalating their activity" and said the threat of attacks were "very specific".
He refused to give further details, but U.S. media reports say Iran has likely moved short-range ballistic missiles to ships in the Persian Gulf that could target United States troops and those of USA allies.
Responding to a question about whether Iraq could protect US interests from attacks by Iran and its proxy forces, Prime Minister Adel Abdul-Mahdi said Tuesday that Iraq takes its responsibilities seriously.
Mr Trump's national security adviser John Bolton said the move sent "a clear and unmistakable message to the Iranian regime that any attack on United States interest or on those of our allies will be met with unrelenting force".
As tensions rise between Washington and Tehran, Baghdad in some ways is caught in the middle. "We've urged the Iraqi government for its own security to get all of those forces under Iraqi central control", Pompeo said.
The US State Department on Thursday warned Iran that any attacks against US interests would incur US response.
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Pompeo also said he wanted to underscore Iraq's need to protect Americans in their country.
In Iraq, a debate has been raging in recent months over the fate of some 5,200 U.S. troops stationed across the country.
Iran, meanwhile, was expected to announced Wednesday that it would partially withdraw from the nuclear deal it struck with world powers in 2015.
Iraq has extensive ties with Iran that go back generations and Iran backs some Iraqi militias. "This is an obligation that Iraq honours", he said.
The Trump administration has imposed sweeping sanctions on Iran, including trying to stop all exports of its oil, although it has issued a waiver for energy-starved Iraq to keep buying power from its neighbour.
Washington has ramped up sanctions on Tehran over its nuclear program in recent months and designated the Iranian Revolutionary Guard Corps as a terrorist group.
Germany has wide disagreements with the Trump administration and along with other European nations still supports the 2015 nuclear deal negotiated under former U.S. president Barack Obama.