Gen. Colin Powell said Friday the United States will leave enough troops in southern Iraq "for some months to come" to pressure Saddam Hussein to step down or agree to a more lasting peace.

Powell, chairman of the Joint Chiefs of Staff, also said U.S. fighter jets will continue to shoot down Iraqi planes that take to the skies.In an hourlong interview with several newspaper reporters, Powell said he was encouraged that the rebellions in northern and southern Iraq have lasted longer and posed a greater threat to Saddam's regime than the United States had expected.

He said world attention and the Americans' presence in southern Iraq mean Saddam "has to be a little careful about how he goes about repressing the various insurrections that are taking place."

But while allied leaders still hope that Saddam will step aside or be overthrown, the shooting down Friday of a second Iraqi warplane in two days does not signify that they will use military force directly to support the rebels, Powell said.

The downings of the two Iraqi planes, he said, stemmed mainly from the allies' determination to enforce the Persian Gulf war's temporary truce, in which Iraq agreed to keep all of its fixed-wing combat aircraft on the ground.

"It does not have to do with us trying to influence the internal battle that is taking place in the country one way or the other," Powell said.

Powell said the allies' main concern was that even though the Iraqi planes were operating several hundreds miles away from U.S. peace-keeping forces in southern Iraq, they suddenly could have made "a dash to the border" to attack allied encampments.

The interview marked Powell's first extended assessment of the seven-week allied war with Iraq and its aftermath. It also provided the clearest statement so far by a high U.S. official of the length of time the Bush administration would keep a U.S. presence in southern Iraq.

Powell said that given the "sustained nature of the insurrections" by the Kurds and the Shiites, "I think Mr. Hussein has a real problem on his hands."

Powell did not specify how many troops the United States will keep in Iraq or how long they will stay there. But he said the Pentagon plans to "continue to withdraw our forces at a pretty good clip" of about 5,000 people a day.

He said 100,000 of the 550,000 U.S. soldiers, sailors and air personnel who waged the war against Iraq have already left the region, and "we have sufficient forces in the theater even at this rapid rate of withdrawal that I'm not worried about us being gone before all this is wrapped up."