The United States has angered Iran, an ally in its war against terrorism, with accusations that it may be trying to destabilise Afghanistan's administration. The claims could cause the first cracks in the alliance against alleged terrorist mastermind Osama bin Laden and his al-Qaeda network, analysts believe. Iran's influential former president Ali Akbar Hashemi Rafsanjani yesterday backed strenuous Foreign Ministry denials by calling US President George W. Bush 'rude and impudent' for the claims. Mr Bush had warned Teheran not to provide al-Qaeda fighters - escaping US air and ground bombardments in Afghanistan - with a safe haven. 'How does Mr Bush dare speak to our nation in such a rude and impudent manner,' Mr Rafsanjani, chief adviser to Supreme Leader Ayatollah Ali Khamenei, told thousands of worshippers during prayers at Teheran University. 'Such threats do not have the intended results.' Iran and the US have a history of animosity. Washington cut diplomatic ties soon after the storming of the US Embassy in 1979 during the Islamic Revolution that overthrew the late shah, who had been a key US ally. Alleged Iranian involvement in terrorism has been the sticking point in the restoration of relations. Teheran is on the US list of nations sponsoring terrorism and was accused of colluding with bin Laden and al-Qaeda in the 1998 bombings of the American embassies in Kenya and Tanzania. But after the September 11 attacks, the US shelved its differences for the fight against terrorism. For 20 years Teheran supported Afghanistan's mujahedeen fighters and then the Northern Alliance. Its involvement on its Western border was crucial in the defeat of Taleban fighters. Since the overthrow of the Taleban, Iran has sent aid and promises of reconstruction and started returning the estimated four million Afghan refugees on its soil. Davood Hermidas Barvand, a professor at Allameh Tabatabi University in Teheran, said Mr Bush's comments were perplexing. 'I do not see any interest whatsoever in Iran harbouring al-Qaeda fighters at present or in the future,' he said. Professor Barvand and The Financial Times newspaper's Teheran correspondent, Guy Dinmore, believe there is a possibility al-Qaeda fighters entered Iran as they fled attacks in November. 'It's quite possible they tried to get out of Iran along well-established drug-smuggling routes,' Dinmore said. 'The big question is whether Iranian authorities would have been in connivance with them.' Dinmore said although the Government was factious, such a possibility was doubtful. Twenty al-Qaeda and Taleban prisoners flown from Afghanistan were due to arrive at the US naval base at Guantanamo Bay, Cuba, yesterday under tight security.