The leader of Iraq's Kurdish region says the US Iraq Study Group report is "unrealistic and inappropriate".
Mr Barzani was the first Iraqi leader to criticised the ISG report
Massoud Barzani was sceptical of plans to involve Iraq's neighbours in peace efforts, and for any weakening down of the Kurds' effective autonomy.
His comments were then echoed by Iraq's Kurdish president, Jalal Talabani, who said he agreed with Mr Barzani.
Earlier, the head of US forces in Iraq said most troops could be withdrawn by early 2008, as recommended.
But the commander, Lt Gen Peter Chiarelli, said such a pullout would only be realistic if Iraq first took significant steps towards political reconciliation.
US President George W Bush has publicly admitted the need for a "new approach" to the conflict in Iraq in the two days since the report was published.
But the president has hinted that he may not accept all of the report's key recommendations.
In the first Kurdish reaction to the Iraq Study Group (ISG) report, Mr Barzani said the Iraq's Kurds were not committed to the report "in any way".
Members of the ISG did not visit Kurdish regions of northern Iraq while compiling their report, Mr Barzani said, calling that a "huge shortcoming".
He was critical of the report's emphasis on strengthening Iraq's central government, apparently "in contrast to the principles of federalism and the constitution, on which the new Iraq is built".
Calling the recommendations "inappropriate", Mr Barzani said: "We do not accept anything that opposes the constitution and the interests of the Iraqi and Kurdistan people."
His stance was backed up shortly afterwards by Iraq's President, Jalal Talabani.
"President Jalal Talabani supports the stand of the president of the Kurdistan region Massoud Barzani on the report," his office said, suggesting some of the reports recommendations ran contrary to Iraqi government policy.
Earlier, Mr Bush said he would work with Republicans and Democrats to find a "new way forward" in Iraq, after meeting congressional leaders in Washington.
Incoming House Democratic leader Nancy Pelosi said Mr Bush had admitted some new tactics might be needed.
Primary mission of US forces should evolve to one of supporting Iraqi army
By first quarter of 2008... all combat brigades not necessary for force protection could be out of Iraq
US must not make open-ended commitment to keep large numbers of American troops deployed in Iraq
Source: ISG report
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Mr Bush is due to meet senior advisers next week to discuss ideas on Iraq.
He will consult US ambassador to Iraq Zalmay Khalilzad, top-ranking state department and military officials and outside experts on Iraq, the White House said.
The main authors of the ISG review of US strategy have urged Mr Bush to follow all of their 79 recommendations.
But Senator Richard Durbin, the second-ranking Democrat in the Senate, said no-one expected Mr Bush to adopt every one of the proposals.
But key themes were important, he said: "We have got to start moving American troops, redeploying them out of Iraq and start bringing them home," he said.
The ISG said the situation in Iraq is "deteriorating" and warned that "time is running out".
Mr Bush is to consult senior officials before announcing his policy
It recommended direct talks with Iran and Syria, and urged Mr Bush to consider shifting US efforts towards the support and training of the Iraqi armed forces.
Mr Bush has said that he will "seriously consider" the report, but he appears already to have ruled out early talks with Tehran and Damascus.
He also appeared to rule out the phasing out of the US combat role in Iraq.
He met UK Prime Minister Tony Blair on Thursday, and pledged a new drive for a peaceful solution to the Israeli-Palestinian conflict.