Turkey's GSM operator Turkcell denies U.S. pressure

"The U.S. has put no written or spoken pressure on Turkcell or made such a statement ... There is no warning on investment (in Syria)," an unnamed Turkcell official was quoted as saying by Reuters.

According to the Reuters article on Wednesday, the U.S. Treasury Department warned American investors in Turkcell, which is both listed on the Istanbul and New York Stock Exchanges, about the company's plan to buy the leading Syrian mobile operator, Syriatel.

Syriatel is at least 69 percent owned by Rami Makhlouf, the cousin of President Bashar al-Assad.

Turkcell is expected to pay approximately $1 billion in cash if the deal of buying most of the shares of Makhlouf, one of Syria's most powerful businessman, goes ahead.

Washington had imposed high-profile sanctions on Makhlouf in February for alleged involvement in public corruption in Syria as relations between the Damascus and the U.S. plummeted.

The U.S. sanctions explicitly state no U.S citizen can do business with Makhlouf. Several Turkcell executives have American citizenship and hold shares in the company, industry sources said in April.

Makhlouf, 39, has denied the U.S. charges, saying he does not have assets in the United States and his businesses that employ thousands of Syrians are legitimate.

A Turkcell-Syriatel deal would be one of the largest in the region's telecom sector. The two companies have a majority share of the market in their respective countries.