Pompeo cancelled talks in Germany to make the four-hour trip to Baghdad -- which has close ties with Iran -- where he met both President Barham Saleh and Prime Minister Adel Abdel Mahdi.

"We talked to them about the importance of Iraq ensuring that it's able to adequately protect Americans in their country," Pompeo told reporters after the meetings.

"They both provided assurances that they understood that was their responsibility," he said.

Pompeo said he made the trip to Iraq because Iran "is escalating their activity," although he declined to discuss intelligence in detail.

"We wanted to let them know about the increased threat stream that we had seen and give them a little bit more background on that so they could ensure that they were doing all they could to provide protection for our team," Pompeo said.

The trip came two days after the United States warned Iran that it would respond with "unrelenting force" to any attack and said the deployment to the region of the USS Abraham Lincoln carrier strike group was meant to send a "clear and unmistakable message" to Tehran.

The tensions come a year after President Donald Trump exited a nuclear deal with Iran and instead launched an aggressive campaign to counter the clerical regime.

Critics both in the United States and abroad say that Trump has sought to ratchet up tensions in hopes of a crisis with Iran, which UN inspectors say is still abiding by the nuclear accord.