US Defence Secretary Mark Esper said on Tuesday that the United States is not pulling its forces out of Iraq, denying that there is a signed letter from the US side announcing an exit."Our policy has not changed. We are not leaving Iraq," Esper told reporters."There is no signed letter, to the best of my knowledge."Earlier Iraqi premier Adel Abdel Mahdi said he had received signed copies of a US letter describing steps to "move out" of the country.