British Foreign Secretary William Hague has spoken with his Iranian counterpart about the crisis in Iraq, the British government said on Monday.
Hague's telephone conversation with Foreign Minister Mohammad Javad Zarif comes amid reports that Tehran is considering providing military support to the Shiite-led administration in neighbouring Iraq, which has come under assault from mainly Sunni militants.
A senior US administration official said talks between the United States and Iran about possible cooperation might take place on the sidelines of nuclear talks in Vienna beginning Monday.
The Foreign Office declined to discuss the content of Hague's call. He was due to brief the House of Commons on the situation later Monday.
A spokesman for Prime Minister David Cameron said: "We have contact with the Iranian government and I think one of the things the foreign secretary will say in the house today is that he discussed a number of bilateral issues, including this, with his Iranian counterpart over the weekend."
Earlier, Hague insisted that Britain would not intervene militarily to help Iraq fight the Islamist insurgents, who have overrun swathes of the country in a matter of days.
"We are not planning a military intervention by the UK in this situation," Hague told BBC radio.
Asked whether Britain could participate in air strikes, Hague said he "could not be clearer" that this would not happen.
"The United States is much more likely to have the assets and capabilities for any outside intervention than the United Kingdom," he said.
But first and foremost the onus lay on the Iraqi security forces to stabilise the situation, he said.
The Iraqi government bore a "heavy responsibility" to try to get a grip on events.
Hague rejected suggestions that the chaotic situation in Iraq was a direct result of the US-British invasion in 2003 which ousted dictator Saddam Hussein.
Mistakes had been made "in the aftermath" of the invasion, but it had not been a mistake itself for Britain to participate.
"It is entirely possible to say it was the right thing to remove Saddam Hussein but that mistakes were made in the aftermath," he said.
Tony Blair, who as prime minister took British forces into war, sparked an angry reaction at the weekend with a 2,800-word essay on his website in which he insisted the current crisis had no link to the 2003 invasion.