WASHINGTON - US President Barack Obama on Friday announced a plan to withdraw most troops from Iraq in 18 months, leaving about 35,000 to 50,000 of the current total of around 140,000 troops behind. The president made the announcement after receiving support from an unlikely quarter - Senator John McCain. "I have chosen a timeline that will remove our combat brigades over the next 18 months," he said in a live-broadcast speech delivered at the Marine base of Camp Lejeune in North Carolina. "Let me say this as plainly as I can: by August 31, 2010, our combat mission in Iraq will end," he said. The president said the remaining troops will "likely be made up of 35,000 to 50,000 troops." He also said the US military mission in Iraq will "change from combat to supporting the Iraqi government and its security forces." The forces to remain in Iraq after August 2010, Obama said, will have three functions, including training Iraqi forces, conducting counter-terrorism missions, and protecting US civilian and military efforts within Iraq. Earlier, Sen McCain and other Republicans emerged from a meeting with Obama at the White House reassured that the president's withdrawal plan is responsible and reasonable. After securing assurances from Obama that he would reconsider his plans if violence increases, McCain and the Republicans expressed cautious support. Speaking on the Senate floor on Friday before the president's speech, McCain credited the opportunity to pull troops out to the surge of troops that President George W Bush ordered two years ago with McCain's support and he cautioned that Iraq remains fragile so Obama should stay flexible and listen to military commanders. "With these factors in mind, I believe the president's withdrawal plan is a reasonable one," McCain said. "Given the gains in Iraq and the requirements to send additional troops to Afghanistan, together with the significant number of troops that will remain in Iraq and the president's willingness to reassess based on conditions on the ground, I am cautiously optimistic that the plan as laid out by the president can lead to success." The convergence of Obama and McCain on Iraq would have seemed highly improbable just a few months ago, when they clashed sharply on the future of the American mission there. McCain accused Obama of being nanve and opposed his withdrawal plans. At one point, McCain said Obama "would rather lose a war than lose a campaign." In his remarks at Camp Lejeune, Obama also said the withdrawal process will go on beyond August 2010. "Under the Status of Forces Agreement with the Iraqi government, I intend to remove all US troops from Iraq by the end of 2011," Obama said, referring to the security pact signed between the Iraqi government and the former Bush administration. The new withdrawal timetable will be three months behind Obama's original pledge to pull out most troops in 16 months after his inauguration. Some 4,250 US troops have died and 650 billion US dollars have been spent since the United States invaded Iraq in March 2003. AFP adds: The president briefed Iraqi Prime Minister Nuri al-Maliki and former US president George W Bush on the new plan by telephone, shortly before making his speech, the White House said. Obama vowed the end of the unpopular war would mean a new era of US diplomacy in the Middle East, which he said would include "principled and sustained engagement" with Iran and Syria. The president also formally announced the appointment of veteran diplomatic troubleshooter Christopher Hill, most recently in charge of talks on North Korea's nuclear programme, as the new ambassador to Iraq. However, some prominent Democrats, including House of Representatives Speaker Nancy Pelosi, have criticised the plan for a "residual force" of soldiers. "I don't know what the justification is for ... the 50,000 troops in Iraq," Pelosi told MSNBC. "I would think a third of that, maybe ... 15,000 or 20,000," would be sufficient, she said. Meanwhile, an American soldier has died after succumbing to wounds he received while on patrol in Baghdad, the US military announced on Friday. The soldier died on Thursday after being injured earlier in the day, a statement said. Meanwhile, a mentally-ill Ethiopian refugee mailed a letter stained with his HIV-positive blood to US President Barack Obama, court records show. Saad Bedrie Hussein told investigators that he mailed the letter " which also contained an orange powdered substance and a photograph of himself taken in Bali " in hopes that he could get tickets to Obama's inauguration. He told police that he "purposely cut one of his fingers with a razor he could bleed on the letter," a criminal complaint said. The letter was addressed to Obama but mailed to the Illinois Department on Aging in Springfield, Illinois and was marked with Hussein's return address. The entire building was locked down for nearly two hours while a hazardous materials team tested the suspicious powder.