2 U.S. Ships on Station Off Colombia for Drug Summit : War on cocaine: The Pentagon cites ‘logistical support.’ Amphibious vessel carries Marines.

The Navy has moved two warships to join a Colombian vessel in the waters off Colombia’s coast as President Bush makes final preparations for Thursday’s drug summit in Cartagena, the Pentagon announced Tuesday.

The U.S. ships, a destroyer and an amphibious assault vessel carrying a complement of Marines as well as helicopters and fighter-attack jets, will provide “logistical support” for the President’s trip, said a Pentagon spokesman, declining to specify what sort of support might be involved.

The American vessels will be accompanied by a Colombian escort ship, he said.

The ship movements are the most visible signs so far of the awidespread concern over Bush’s security during the eight-hour visit to Colombia, the site of repeated bombings and other acts of violence related to the U.S.-backed crackdown on the nation’s powerful cocaine cartels.

Some senior White House aides argue that the concerns have been overplayed and that the trip poses little real danger to Bush. But for the Secret Service, which believes that the best means of protection is to keep the President away from threatening situations, the trip has become a headache.

At the White House, National Security Adviser Brent Scowcroft conceded Tuesday that the trip “is an unusual situation.” Even so, he insisted, “we’re comfortable about the President’s security.”

Whatever threats exist, Scowcroft said, “we think they’re adequately taken care of.”

Although Thursday’s summit has been the subject of elaborate planning, the actual event may be far less dramatic. White House officials have spent several days cautioning reporters against expecting major advances from the summit.

Government officials representing Colombia, Peru and Bolivia, the three South American countries participating in the session, hope to use the summit to press the United States to provide considerably more financial assistance than the Administration is willing to give.

Colombia’s leaders have worked with the U.S. government in attacking their drug-trafficking cartels, which pose a serious threat to the government in Bogota. Peru and Bolivia, in contrast, have been less enthusiastic about moving against their primary contribution to the drug problem--the hundreds of thousands of peasants who depend financially on cultivation of coca leaf.

The Administration has said it will not provide additional economic assistance until next year, after the nations have demonstrated their determination to wage a sustained anti-drug crackdown.

Another point of tension is continued sensitivity about the use of U.S. military force in the region. Bush probably will discuss the question of increased military cooperation with Colombian President Virgilio Barco Vargas during the summit, Scowcroft said. But, he noted, the subject is unlikely to be resolved during the meeting.

The Administration would like to station U.S. warships permanently off the Colombian coast to help establish a “radar net” that would track airplanes carrying drug shipments north. But such plans are “on the shelf” after publicity earlier this year caused heated Colombian objections, Scowcroft said.

“It was felt that could be best done after the summit rather than in the summit,” said one senior official. There could be an “agreement in principle” on the issue, the official added, saying that Bush and Barco might “agree on the climate and the process and then just let it take its course quickly after that.”

For the “logistical support” assignment, the Navy has chosen the amphibious ship Nassau, based in Norfolk, Va. It can carry more than 1,900 Marines and act as base to 21 helicopters and 10 AV-8B Harrier fighter-attack jets. A Pentagon source confirmed that Marines from Camp Lejeune in Jacksonville, N.C., are aboard the Nassau but would not say whether the ship is carrying its full complement.

Accompanying the Nassau is the destroyer Sampson, based in Mayport, Fla., and armed with ship-attack missiles and torpedoes.

Times staff writers Melissa Healy and Douglas Jehl contributed to this story.