FILE PHOTO: Iran's President Hassan Rouhani speaks at a news conference on the sidelines of the 73rd session of the United Nations General Assembly at U.N. headquarters in New York, U.S., September 26, 2018. REUTERS/Brendan Mcdermid/File Photo

DUBAI (Reuters) - Iran said that the U.S. military presence in Syria had been “a mistake, illogical and a source of tension”, in Tehran’s first reaction to President Donald Trump’s planned pull-out.

Trump has begun what will be a total withdrawal of U.S. troops from Syria, saying on Wednesday they had succeeded in their mission to defeat Islamic State and were no longer needed in the country.

“From the start, the entry and presence of American forces in the region has been a mistake, illogical and a source of tension, and a main cause of instability,” Iranian Foreign Ministry spokesman Bahram Qasemi was quoted as saying by state media on Saturday.

Trump said in a tweet on Thursday that “Russia, Iran, Syria & many others are not happy” about the planned U.S. withdrawal.

Iran, a key supporter of President Bashar al-Assad in Syria’s civil war, has sent military “advisers” as well as military equipment and regional Shi’ite militias to fight anti-government groups.

Tehran has opposed the presence of foreign forces in Syria, except those -- from Iran and Russia -- which have been invited by the Assad government.