From ABC News March 18:

President Obama told a bipartisan group of members of Congress today that he expects the U.S. would be actively involved in any military action against Libya for “days, not weeks,” after which he said the U.S. would take more of a supporting role, sources tell ABC News.

The White House meeting with 18 lawmakers came as Obama delivered an ultimatum to Libyan leader Moammar Gadhafi that he must immediately implement a ceasefire in all parts of Libya and allow international humanitarian assistance, or risk military action against his regime.