WASHINGTON, Sept. 26 — Defense Secretary Robert M. Gates told Congress on Wednesday that he envisioned keeping five combat brigades in Iraq as a “long-term presence.”

Mr. Gates told the Senate Appropriations Committee, “When I speak of a long-term presence, I’m thinking of a very modest U.S. presence with no permanent bases, where we can continue to go after Al Qaeda in Iraq and help the Iraqi forces.”

He added that “in my head” he envisioned a force as a quarter of the current combat brigades.

There are now 20 combat brigades in the country, a number that is scheduled to drop to 15 by next summer. Mr. Gates has previously expressed hope that if security conditions in the country continue to improve, force levels in Iraq could drop to 10 brigades by the end of 2008.

Mr. Gates gave no timetable for reaching that force level or for how long the forces would be required to stay. He added that there had been no detailed planning by the Pentagon about what level of forces would be required on a more or less permanent basis.