The ISG warns of the risk of a slide towards a humanitarian catastropheUS President George W Bush is due to meet Tony Blair at the White House for talks expected to focus on the findings of a major review of US policy in Iraq.
The Iraq Study Group (ISG) urged talks with Iran and Syria on tackling Iraq's unrest, a move Mr Bush has resisted.
Mr Blair intends to mirror the call for Iraq to be seen as part of a wider Middle East plan, correspondents say.
Syrian Information Minister Mohsen Bilal said Syria welcomed the report and had always been open to talks.
He said: "Syria has never stopped the dialogue, but we say to those who stopped the dialogue and are now coming back to it: better late than never."
Middle East trip
The ISG's assessment of the Bush administration's policy in Iraq is scathing, saying the situation there is "deteriorating" and warning that "time is running out".
It says US troops should be withdrawn from combat and instead used to train Iraqis.
While it offers no hard timetable for a pullout of US forces, the review does say combat troops could withdraw by early 2008.
The BBC's Justin Webb in Washington says that, for an increasingly lonely Mr Bush, the presence of Mr Blair, a friendly face and an able advocate for the cause, will be very welcome.
But, our correspondent adds, the time needed for the White House to consider the report fully will mean a period of uncertainty that could stretch to weeks.
Analysts say Mr Bush will want to refer to his own policy review, being carried out by the National Security Council, and another being conducted by the Pentagon before announcing major policy changes.
Along with recommendations on changes to policy in Iraq, the report also calls for action on finding an end to the long-running conflict between Israel and the Palestinians.
The BBC's political correspondent Nick Robinson, who is travelling with Mr Blair, says the UK leader is expected to announce that he will be travelling to the Middle East shortly with that aim in mind.
Israel's Prime Minister Ehud Olmert has rejected the ISG's assessment that progress in Iraq is linked to resolving the conflict between Israel and the Palestinians - although he said he was interested in re-starting peace talks.
But he ruled out opening peace talks with Syria in the near future, as recommended in the report.
No quick fixes
The ISG report was published on the day that Robert Gates was confirmed as the new US defence secretary. He has acknowledged the US is not winning the war in Iraq and has stressed he is open to new ideas.
Correspondents say the review offers no big surprises and no quick fixes.
The 142-page report includes 79 recommendations, of which three are key:
- A change in the primary mission of US forces in Iraq to enable it to begin to move combat forces out responsibly
- Prompt action by the Iraqi government to achieve reconciliation
- New and enhanced diplomatic efforts in the region
The Iraqi government welcomed the review.
Deputy Prime Minister Barham Salih said the proposals were in line with the government's view that security must be transferred to Iraqis.
However, a spokesman for the main Sunni bloc in parliament said the report should have included a specific timetable for a US withdrawal.