In the letter, Lantos, of the Democratic Party, said that the visit by Hamas political leader Halid Mashaal to Ankara would harm Turkey’s national interests, the fight to combat terrorism and Turkish-US relations.

Lantos said that although the messages given by Turkey could be right the meeting between Foreign Minister Abdullah Gul and Mashaal last Thursday had the reserve effect and had weakened the power of Palestinian leaders calling on Hamas to end its polices of violence and non-recognition of the state of Israel.

Describing Hamas as “a gang of terrorists”, Lantos said the group, which was swept to power in Palestine after winning recent national elections, was “refusing to recognise the right of the existence of Israel” and of calling Jews “children of pigs and monkeys.”

“While your officials are getting closer to the Palestine version of Ocalan (the imprisoned leader of the terrorist group the PKK), Mashaal, who are you going to retain your virtuous position in your fight against the PKK?” Lantos asked Erdogan in his letter. However, the congressman stressed that the US supported Turkey in its fight against separatist terrorism.

Lantos said that he met the newly appointed Turkish ambassador to the US a week ago and his re-assurance that Ankara would side with the US on foreign policy has been breached in less than a week.

The Californian congressman had been a strong advocate of the Turkish position rejecting claims that the Ottoman government had committed genocide against its Armenian citizens during the years of World War One. However, Lantos last year withdrew his support to Turkey on the Armenian question after Ankara refused to side with the US on the Iraq war.