The Reagan administration yesterday backed away from its campaign to close Beirut International Airport, shifting its efforts to negotiating improvements in airport security with the Lebanese government.

White House spokesman Larry Speakes said the administration has discussed specific steps with the Lebanese government, including a ban on all militias at the airport, a ban on all weapons and an "effective" security force to maintain control there.

"We're indicating to them what we want and they're claiming they're making some steps," Speakes said.

Until now, the administration appeared to focus on ways to close the airport, mainly through an international boycott. But Speakes made no mention of this yesterday and indicated that adequate security measures would satisfy the United States.

Lebanese sources said the Beirut press reported yesterday that among the steps the United States had suggested is the stationing of several hundred U.N. troops at the airport. But Lebanese Ambassador Abdullah Bouhabib said his government has not decided to ask the U.N. for such help.

Bouhabib also said that U.S. officials had initially told him that the U.S. sanctions on the airport and on Lebanon's state-run Middle East Airlines were "temporary" and would be lifted once security measures at the facility were improved.

This seemed to suggest the administration had never intended to push its allies hard to join in the boycott of the airport, but was using it to pressure Lebanon.

Speakes added that the United States welcomes the plan announced Tuesday by Lebanese leaders to improve security in West Beirut and at the airport but said "they have not done enough yet."

The plan, worked out under Syrian guidance in Damascus, calls for disarming the militia forces, setting up a security coordinating committee of their leaders with Syrian observers, and establishing a 5,000- to 10,000-man Moslem-Christian army unit to assure security in west Beirut and at the airport.

The administration's public shift from its announced objective came as Vice President Bush indicated that there was "a division" among the United States' European allies over whether to follow the American lead in boycotting the Beirut airport and canceling landing rights for Middle East Airlines.

Speaking at a National Press Club luncheon, Bush said he would prefer to see the various Lebanese militias acting together to safeguard the airport "and thus not have us have to go forward on our own." He added that the United States is ready to work with its European allies, "although there's a division still there as to how far they want to go to take action."

A European diplomat said he had noticed "a certain frustration" in the administration over the failure of any Western European country to respond really positively to the U.S. call for a boycott of the Beirut airport.

Despite signs that the administration had run into trouble in its drive to organize a boycott of Beirut airport, U.S. officials continued to insist the U.S. pressure is having a beneficial effect.

A senior administration official said the United States is getting far more private than public support from its European allies. "The reason that the Lebanese are being responsive is that we are getting this private support," he said.

Meanwhile, Bush named retired admiral James L. Holloway, former chief of naval operations, as executive director of a task force to examine how the United States can combat terrorism.

Bush said the panel, created by President Reagan during the hijacking of Trans World Airlines Flight 847 last month, will submit a report before the end of the year. He said the panel likely will suggest better international cooperation on sharing intelligence and on extradition requests.

In a speech and question-and-answer session at the press club, Bush said, "We'd like to find a way to be as surgical as possible" in retaliating against terrorists.