WASHINGTON (AP) _ U.S. troops have ''started to move more aggressively'' to disarm Haitian paramilitary thugs and can do the job with or without help from Haiti's military, the American commander in Haiti said today.

Administration officials said Sunday that there has been no change in its policy of having U.S. troops function as police, leaving Haitian authorities responsible for retrieving weapons from armed civilians.

Lt. Gen. Hugh Shelton, the U.S. military commander in Haiti, said today his forces ''have gotten good cooperation'' from Haitian dictator Raoul Cedras, ''but in terms of disarming the paramilitary system, the attaches, that exists here, that's been going slower that we would like for it to.''

''We in fact have started to move more aggressively,'' Shelton said on CBS. ''We've started to go after the attaches and in fact during last couple of days we picked up four of the top thugs ... who we were looking for on the streets and we're starting to dismantle that organization as we speak.''

Asked if U.S. forces would disarm the paramilitary forces without help from Cedras, Shelton said ''we certainly would like to do it in cooperation with the Haitian military.... but I have made it quite clear if that institution is to survive we need to be more aggressive in getting the violence off the streets, which means disarming those who are not authorized to have automatic weapons.''

White House Chief of Staff Leon Panetta, speaking on CBS' ''Face the Nation,'' said that U.S. forces will be a ''little more aggressive'' in disarming Haitians but that the main thrust will be working through the Haitian military.

But Sen. Christopher Dodd, D-Conn., part of a six-member Senate delegation that returned from Haiti Sunday, said that if cooperation with the Haitian military doesn't work, U.S. forces ''are going to disarm them one way or another.''

''They're trying to work with the Haitian military,'' Dodd said today of the U.S. forces. ''Remember, not every single member of the Haitian military is bad. There are people there we can work with. ...''

He told CBS on Sunday there is a ''real effort right now to get at the cache of arms, to get the weapons'' that could be used to prolong the violence against democratic forces in Haiti.

A critic of the administration's policy, Rep. Newt Gingrich, R-Ga., said that determination to stop Haitian-on-Haitian violence was a ''disaster in the offing'' and urged a rapid withdrawal of U.S. troops.

Appearing on NBC's ''Meet the Press,'' Gingrich said that by aggressively going after Haitian gunmen, ''we are right now drifting steadily into a quicksand of misery, and I think that this is an enormous miscalculation by the Clinton administration.''

He said the administration was ''now on the edge of disaster'' and urged that U.S. troops be pulled out ''as quickly as possible, and I mean weeks - not months, not years.''

The House is expected to vote this week on several resolutions, including one authorizing the U.S. military presence in Haiti until March 1. House Speaker Thomas S. Foley, D-Wash., speaking on NBC, said he opposed setting a ''date certain'' for withdrawal but that he thought the March 1 bill would pass.

The Senate is also likely to debate the issue, although Dodd said his delegation to Haiti all agreed with the military that putting a time limit on the mission would endanger the troops.

''I don't know of anyone in the U.S. Senate who wants to be in the position of putting a date certain in the resolution and jeopardizing the lives of these men and women,'' he said.

The Pentagon, meanwhile, said all 1,800 U.S. Marines in Haiti will begin to withdraw from the Caribbean country starting today.

The Marines handed over responsibilities for the northern port of Cap- Haitien to soldiers of the U.S. Army 10th Mountain Division on Sunday afternoon, said a Pentagon spokesman, Army Lt. Col. Roger Kaplan.

Deputy Defense Secretary John Deutch said on CNN that the Marine withdrawal was possible because the Haiti operation has been ''so successful.''

Nearly 21,000 U.S. soldiers and Marines were in Haiti as of Sunday, military officials said.