Longstanding friction between US President Donald Trump and two top aides, the National Security Adviser and the Chief of Staff, has grown to a point that either or both might quit soon, four senior administration officials said.Both H.R. McMaster and John Kelly are military men considered by US political observers as moderating influences on the president by imposing a routine on the White House. They have also convinced Trump of the importance of international alliances, particularly NATO, which he has criticized as not equally sharing its burdens with the United States.However, all the officials were quick to add that the tensions could blow over, at least for now, as have previous episodes of discord between the president and other top officials who have fallen out of favor, including Secretary of State Rex Tillerson and Attorney General Jeff Sessions.Asked about sources saying that either National Security Adviser McMaster or Chief of Staff Kelly, or both, might be leaving, White House spokesman Raj Shah on Thursday did not address the possibility. He said, "the president has full confidence in each member of the team." Press secretary Sarah Sanders said on Tuesday that Trump "still has confidence in General McMaster."Neither Kelly nor McMaster responded to requests for comment on whether they would remain in the administration.