Despite a tight economic embargo, the Clinton administration has agreed to allow Boeing Co. to provide Iran's national airline with parts to ensure the safety of its Boeing 747 passenger aircraft, administration officials said.

Ending months of internal debate, Deputy Secretary of State Strobe Talbott decided two weeks ago to grant a special license for Boeing to provide Iran Air with kits to prevent engines from falling off older 747s in flight, administration officials said.

The Federal Aviation Administration ordered the modifications following the October 1992 crash of an El Al cargo jet that slammed into an apartment complex in Amsterdam, killing more than 50 people, after two engines ripped off its wing.

Notwithstanding the FAA order, administration officials said they were extremely cautious in deciding whether to permit Boeing to provide aircraft parts to a country they regard as synonymous with state-sponsored terrorism--in part because Iran Air planes are thought to have been used to ferry terrorists and explosives around the world. But in the end, they said, they decided they had little choice but to grant the waiver, given the risk of a crash that could claim hundreds of innocent lives.

"There's always a risk that any Iran Air plane, civilian or cargo, can be used for nefarious purposes, but the greater risk in our view would have been the possibility of a catastrophic accident killing civilians," said a senior administration official who described the decision, which has not been publicly announced. "The overriding concern is air safety."

The official said the waiver was carefully written to ensure that the modification kits can be installed only on seven Iran Air 747s used for carrying passengers, rather than cargo jets that could be used for military purposes. Nor will Iranians be given access to the highly specialized tools used to perform the modifications, U.S. and Boeing officials said, because the work will be carried out by a contractor--probably the German airline Lufthansa--in Europe.

The deliberations surrounding the waiver--which was reviewed by three different State Department offices as well as by Secretary of State Madeleine K. Albright--reflect the extraordinary sensitivity of administration policy toward Iran. State Department officials are particularly concerned about how the waiver will be received on Capitol Hill and, following a reporter's inquiries, made plans to brief staff members of key congressional committees before the news became public.

In a brief statement Thursday, State Department spokesman James P. Rubin emphasized that the waiver was not intended as a political gesture. "The American government seeks to ensure safe air travel for citizens of all nations," he said. The waiver, he added, "should not be viewed in terms of political content or messaging."

In 1995, President Clinton cited Iranian support for terrorist groups in banning all U.S. trade with the Islamic Republic, although the sanctions were subsequently relaxed to permit the sale of food and medicine. U.S. companies have the right to apply for waivers to supply other goods to Iran, but they are granted only in rare cases, officials said.

This will apparently be one of those cases. Following the El Al crash, the FAA ordered Boeing to modify the pylons, or struts, used to attach engines to the wings of 747 jumbo jets. The FAA's European counterpart adopted the same standard. Failure to complete the modification could ultimately prevent planes from using runways in Europe or the United States.

Boeing has been providing the kits, whose cost runs to six figures each, free of charge to carriers worldwide, said Boeing spokesperson Virnell Bruce. Iran Air sought to acquire the kits through a London intermediary, which subsequently hired a Washington law firm, Williams & Connolly, to apply for the special license, Bruce said. A spokesman for the law firm declined to comment on its role.

The application was initially made to the Treasury Department's Office of Foreign Assets Control. Treasury referred it to the State Department, which ultimately approved the request last month. State Department officials said they took pains to make sure that the kits will be matched to the specific tail numbers of 747s used by Iran Air to carry passengers.

"That was done to minimize the risk we'd make safer those cargo planes that could be used to ferry arms," the senior official said.