The White House was made aware ahead of time that Sen. John McCain, R-Ariz., would travel to Syria this week, White House spokesman Jay Carney said Tuesday.

Carney said the president looks forward to speaking with McCain about the trip, but referred all questions regarding its details to the senator's office.

McCain crossed into Syria from Turkey on Monday for several hours to meet with rebel forces. In meetings with McCain, rebel leaders called for greater support from the United States, including the arming of the rebel forces, airstrikes against the Syrian national army and the enforcement of a no-fly zone.

The Arizona senator is the highest ranking U.S. official to visit Syria since the civil war began.