Iranian Foreign Minister Manouchehr Mottaki charged on Monday that US and British forces are fomenting terrorism in the region. Mottaki's comments came as US Defence Secretary Robert Gates made an unannounced visit to Afghanistan ahead of a trip to Kabul by Iranian President Mahmoud Ahmadinejad. "I accuse the US, Britain and their forces in Afghanistan and Pakistan of fomenting terrorist acts in the region," Mottaki told a regional energy conference in Tehran. Ahmadinejad was to visit Iran's eastern neighbour later on Monday to discuss with his counterpart Hamid Karzai how to stabilise the war-torn nation. The two leaders are to "examine solutions to Afghanistan's problems" as Iran seeks to boost relations, Iran's Mehr news agency reported on Sunday. Ahmadinejad and other Iranian officials have repeatedly called for the withdrawal of US-led forces from Afghanistan, saying their presence is stoking the Taliban insurgency. But despite their rivalry, Washington and Tehran are both sworn enemies of the extremist Sunni Muslim militia which ruled in Kabul from 1996 to 2001, before being overthrown in the US-led invasion. The United States has made a number of efforts to involve all of Afghanistan's neighbours, including Iran, in restoring stability to the country. But they have been complicated by the lack of diplomatic relations between Tehran and Washington and the standoff over Iran's nuclear programme. Shiite Iran, which has close ethnic and religious ties with Afghanistan, has long suffered from the effects of opium production in its eastern neighbour, with easily available heroin fuelling a big rise in drug use at home. Afghanistan is the source of 90 percent of the world's heroin.