Tehran - Turkish efforts to improve Tehran-Washington ties were dampened Wednesday when Iran's leader said that no change has yet been witnessed in the policies of US President Barack Obama.

"The US government is continuing its previous course and there are no signs indicating that the Americans would make up for their previous mistakes," Iran's Supreme Leader Ayatollah Ali Khamenei told visiting Turkish President Abdullah Gul.

Gul is currently in Tehran to attend the 10th summit of the Economic Cooperation Organization (ECO), but the visit has been overshadowed by press reports that Gul would deliver a message from Obama to his Iranian counterpart Mahmoud Ahmadinejad.

"The US has committed grave mistakes in Afghanistan and Iraq and another one in the Gaza Strip," said Khamenei, who according to the Iranian constitution has the final say on all state affairs.

The government of Turkey has reportedly agreed to act as mediator between the two countries but the mediation role has never been confirmed by any of the relevant officials.

Gul said before his departure to Tehran that Iran should review its political stance, adding that the arrival of Obama in the White House had been very important and that as a result "all countries must rethink their policies."

Washington has indicated plans to change its policy toward Tehran and resume direct talks after three decades of diplomatic estrangement.

Tehran has welcomed the plan but says that future relations should be based upon mutual respect and US acknowledgement of Iran's international rights, including the pursuing of its controversial nuclear programme. (dpa)