Prime Minister Gordon Brown said on Saturday he wanted to reduce British troop levels in Iraq but he refused to set any timetable for their departure. Making an unannounced visit to Baghdad, Brown was also expected to seek to build on vastly improved security in Iraq to promote investment. Britain sent 45,000 troops to take part in the 2003 US-led invasion to topple Saddam Hussein, but only some 4,000 remain at an airport near the southern city of Basra where they are training Iraqi security forces. “It's certainly our intention that we reduce our troop numbers but I'm not going to give an artificial timetable for the moment,” Brown told reporters travelling with him after meeting Prime Minister Nuri Al-Maliki. “The tests for us will be how are we meeting the objectives that we've set. What progress can we show?” Brown's visit coincides with the Iraqi government's growing confidence in its ability to secure the country. That was reflected in an agreement this week by Maliki and US President George W. Bush to set a “time horizon” for reducing American forces in Iraq. It was the closest the Bush administration has come to acknowledging the need for a timeframe for US troop cuts. Bush has long opposed deadlines for troop withdrawals. Brown's government, whose opinion poll ratings have slumped, is expected to make a statement to parliament next Tuesday on Britain's future role in Iraq. Britain announced last October it planned to cut troop numbers to 2,500 from around April this year, cutting back its involvement in a war that is unpopular with many Britons. But the government delayed the move after Shi'ite militias fiercely resisted an Iraqi military crackdown in Basra province in late March. Brown said key objectives that needed to be met for reducing troop numbers included training Iraqi forces, making sure Iraq could push forward with local elections expected this year and also in boosting development in Basra, the country's oil hub. Maliki backs Obama plan Iraqi Prime Minister Nuri Al-Maliki told a German magazine he supported prospective US Democratic presidential candidate Barack Obama's proposal that US troops should leave Iraq within 16 months. In an interview with Der Spiegel released on Saturday, Maliki said he wanted US troops to withdraw from Iraq as soon as possible. “US presidential candidate Barack Obama talks about 16 months. That, we think, would be the right time-frame for a withdrawal, with the possibility of slight changes.” It is the first time he has backed the withdrawal timetable put forward by Obama, who is visiting Afghanistan and us set to go to Iraq as part of a tour of Europe and the Middle East. Obama has called for a shift away from a “single-minded” focus on Iraq and wants to pull out troops within 16 months, instead adding US soldiers to Afghanistan. Asked if he supported Obama's ideas more than those of John McCain, Republican presidential hopeful, Maliki said he did not want to recommend who people should vote for. “Whoever is thinking about the shorter term is closer to reality. Artificially extending the stay of US troops would cause problems.” Maliki, who is due to visit Germany this week, has suggested a timetable should be set for a US withdrawal but US officials have been more cautious, despite an improving security situation.