TUNIS, Sept 12 (Reuters) - The United States and five European powers called on Monday on forces loyal to eastern Libyan commander Khalifa Haftar to withdraw from several key oil ports seized from a rival force over the weekend.

“We call for all military forces that have moved into the oil crescent to withdraw immediately, without preconditions,” said the statement from the United States, France, Germany, Italy, Spain and Britain.

Forces loyal to Haftar took control of Ras Lanuf, Es Sider, Zueitina and Brega ports, displacing a force that is allied to the U.N.-backed government in Tripoli.