The ruins of West Beirut barely have stopped smoldering since the latest cease-fire, but Lebanese and foreign experts already are drawing up plans for a $2 billion reconstruction project to be financed with Arab oil money.

At the initiative of Persian Gulf Arab oil-producing states, a team of architects and engineers Saturday began to tour damaged neighborhoods of West Beirut, where thousands of Palestinian guerrillas are still trapped by Israeli forces surrounding the capital.

The team plans to make a report within a week roughly estimating the scope of the work to be done. Sources familiar with the project said the Arab states have expressed willingness to put up $2 billion and that the work would probably cost at least that much.

Palestine Liberation Organization officials have criticized Arab governments sharply for failing to come to their aid in Beirut. Now that a political solution of the crisis seems to be within reach, the wealthy Arab states want to salve their consciences somewhat by helping the Lebanese rebuild, the sources said.

The prospective financiers are said to want an initial master plan within a month showing the areas that will have to be razed and presenting ideas for new residential and office districts. Focus of the project is to be the besieged, predominantly Moslem western sector of Beirut, but damaged neighborhoods in mainly Christian East Beirut also would be rebuilt, the sources said.

They said detailed planning would take at least 1 1/2 years, after which construction could begin.

The team of experts includes four Lebanese -- two Moslems and two Christians -- plus a European architect who specializes in the reconstruction of war-damaged cities.

Another team has been assigned to do a similar study by the United Nations but has been delayed by its inability so far to get permissions from the officials involved.

"I was shocked by what I saw," the European architect said after touring devastated neighborhoods near the National Museum, the main crossing point between East and West Beirut.

"It was very depressing," said the architect who declined to be identified. "It reminded me of films of Berlin in 1945."

Of 32 buildings he inspected on either side of the Green Line near the museum crossing, 21 of them will have to be razed, he said.

The Lebanese team members have estimated that up to 30 percent of the buildings in West Beirut have been destroyed by two months of bombardment by the Israeli Air Force, Army and Navy. While many are still standing, they are too damaged to be renovated and must be razed, the experts said.

On Saturday, the team found a group of Palestinian fighters in an unsafe building and advised them to vacate it, one of the architects said. The guerrillas filed out with their weapons and belongings, then stood in the street looking expectantly.

"Where should we go?" one of the fighters asked. The architect looked around, pointed out another shell-damaged but safer building and the fighers obediently moved into it.

A similar offer was made to Israeli troops, but they politely turned it down.