Baghdad - American diplomats and army commanders have held indirect talks with insurgents in Iraq, the first officially sanctioned contact between the two sides in two years of violence.

A US embassy official in Baghdad said efforts were under way to "engage" elements of the resistance in an apparent softening of the Bush administration's opposition to negotiations.

"In order to achieve stability and [an] end to the insurgency and stop Iraqis from being killed in large numbers, the insurgency has to be addressed," the official told reporters.

"I don't think the people we are sitting in the room with are directly operational, but they have relationships with them, sometimes through family ties, sometimes through previous associations with the previous regime."

The briefing was on the record but under embassy rules the official could not be named.

He did not elaborate on the substance of the talks and it was unclear which of the insurgency's numerous groups had been engaged.

The contacts, conducted mainly through Sunni Arab tribal and religious leaders, were limited to factions which could be coaxed away from violence and into mainstream politics, the official added.

That ruled out Abu Musab al-Zarqawi's al-Qaida in Iraq and other radical Islamic groups believed responsible for most of the suicide bombings. "Some insurgents are irredeemable and have to be dealt with in a purely military way."

The US has made public overtures to Iraq's Sunni Arabs, a disaffected minority driving the insurgency, but until now drew the line at contacts with the "terrorists" denounced by President Bush.

The administration has come under increasing pressure to show progress in a war which claims approximately two American lives daily and is blamed for shortfalls in army recruitment.

A recent Gallup poll showed 57% of Americans do not believe it was worth invading in March 2003.

It is no secret that some US commanders on the ground have informal and indirect contacts with their opponents, mostly via Sunni mosques and tribal elders. The embassy official suggested those channels have become more formalised.

The insurgency is a complex mix of criminal gangs, Sunni Arab nationalists, former members of Saddam Hussein's Ba'ath regime and Islamic radicals, with many foreigners among the latter.

Two years ago Mr Bush's response was "Bring 'em on". But as casualties soared and the nascent Iraqi state reeled, the US reached out to the Ba'athists and Sunnis, encouraging, for example, the country's new Shia and Kurdish rulers to scale back purges known as "de-Ba'athification".

Earlier this week an Arab Sunni politician and former electricity minister, Ayham al-Samarie, said two groups, the Islamic Army in Iraq and the Army of Mujahideen, were ready to talk to the government.

The prime minister, Ibrahim al-Jaafari, said yesterday he hoped to draw "all sectors" of Iraqi society into the political process and hinted that this included homegrown insurgents.

The ruling Shia and Kurdish coalition promised to give Sunni Arabs a greater role in writing a new constitution by increasing their membership on the drafting committee, where they occupy two out of 55 seats.

Some officials said Sunnis would be given an additional 13 seats, matching Kurdish representation, but President Jalal Talabani, himself a Kurd, said the government would meet Sunni demands for an extra 20 to 25 seats.

The British foreign secretary, Jack Straw, visiting Baghdad as part of a European Union delegation, expressed confidence that Iraq would have a referendum-approved constitution and elections by the end of the year. The delegation also pledged financial support for Iraq.