The chief of the US Central Intelligence Agency [CIA] has sent a letter to Iranian Major General Qassem Soleimani and Iranian leaders to warn against Tehran's increasingly threatening behaviour in Iraq, reports said on Saturday.
Mike Pompeo revealed the move during a panel at the annual Reagan National Defence Forum in Southern California, where he said he sent the letter after the senior Iranian military commander indicated that forces under his control might attack US forces in Iraq.
"What we were communicating to him in that letter was that we will hold he and Iran accountable for any attacks on American interests in Iraq by forces that are under their control," Pompeo told the panel.
"We wanted to make sure he and the leadership in Iran understood that in a way that was crystal clear."
But Soleimani, who is the commander of foreign operations for Iran's elite Revolutionary Guards, allegedly refused to open the letter, according to Pompeo, who took over the CIA in January.
The news was reiterated by Iranian media who reported an unnamed CIA contact attempted to pass on a letter to Soleimani when he was in the Syrian town of Albu Kamal during the fighting against the Islamic State group in November.
"I will not take your letter nor read it and I have nothing to say to these people," Mohammad Mohammadi Golpayegani, a senior aide to Supreme Leader Ayatollah Ali Khamenei, quoted Soleimani as saying, according to the semi-official news agency Fars.
In October, Soleimani warned Kurdish leaders in northern Iraq to withdraw from the oil city of Kirkuk or face an onslaught by Iraqi forces and allied Iranian-backed fighters, Reuters reported.
"You need to only look to the past few weeks and the efforts of the Iranians to exert influence now in Northern Iraq in addition to other places in Iraq to see that Iranian efforts to be the hegemonic power throughout the Middle East continues to increase," Pompeo said.
The presence of Soleimani on the frontlines highlights Tehran's heavy sway over policy in Iraq, and comes amid its ongoing proxy war with regional rival Saudi Arabia.
The CIA chief said Saudi Arabia has grown more willing to share intelligence with other Middle Eastern nations regarding Iran and Islamist extremism.
Last month, the Israeli government said that Israel had covert contacts with Saudi Arabia amid common concerns over Iran, a first disclosure by a senior official from either country of long-rumoured secret dealings.
"We've seen them work with the Israelis to push back against terrorism throughout the Middle East, to the extent we can continue to develop those relationships and work alongside them - the Gulf states and broader Middle East will likely be more secure," said Pompeo.
Agencies contributed to this report.