Outlining a timetable for withdrawal from Iraq, Gordon Brown has said British troops will "leave Iraq a better place".
The prime minister was speaking after talks in Baghdad with Iraqi leader Nouri Maliki.
In a joint statement, they said that the "role played by the UK combat forces is drawing to a close".
"These forces will have completed their tasks in the first half of 2009 and will then leave Iraq," it added.
The United Nations mandate for coalition forces in the country expires at the end of the month, and the Iraqi council of ministers has agreed to allow British troops to remain in the country until the end of July.
The deal allows for the Iraqi government to request an extension of the UK military presence, but this is not expected to be used.
Brown said that "the mission will end no later than the 31st of May next year".
"Our troops will be coming home within the next two months [after that]," he added.
"The biggest reduction will be at the end part of the period we are talking about."
The prime minister added: "It is important to remember we have been engaged in the most difficult and challenging of work.
"The tasks of overthrowing a dictatorship, the task of building a democracy for the future and defending it against terrorism."
"We have made a huge contribution and of course given people an economic stake in the future of Iraq. We leave Iraq a better place."
Dods Parliamentary Communications Ltd