WASHINGTON (Reuters) - The United States relaxed sanctions on four large banks in Myanmar on Friday, allowing them access to the U.S. financial system as a reward for the country's political reforms. The Treasury Department issued a general license to the Myanma Economic Bank, Myanma Investment and Commercial Bank, Asia Green Development Bank and Ayeyarwady Bank. A general license eases restrictions and lets the banks deal with U.S. citizens and companies, but leaves sanctions laws on the books, giving Washington leverage should Myanmar start to backslide on reforms. ...