Questions mount as Hasenfus trial starts in Managua. Despite US denials, doubts raised that supply operation can work without CIA

The broad outlines of a sophisticated resupply operation to Nicaraguan rebel groups are coming into sharper focus. The Reagan administration has denied any connection with a purportedly private effort designed to sustain the six-year contra war against Nicaragua's Sandinista government.

But two weeks after the downing of an American supply flight, signs are emerging that point to the likelihood of official United States involvement.

``It's a little hard to imagine that the CIA would not have some role in facilitating the movement of supplies shipped through El Salvador's Ilopango air base,'' says former Central Intelligence Director Stansfield Turner. ``The CIA can wink at the Salvadorean commander and say, `I don't know where the plane is going, but let it go.' ''

Of the likelihood that supplies could be shipped through Ilopango without some official US participation, retired US Army Lt. Col. Ed King says, ``It's theoretically possible, but as a practical matter it's almost impossible.'' Mr. King, whose military career included high-level positions in inter-American organizations, testified before the House Foreign Affairs Committee last week.

Ilopango, the headquarters of the Salvadorean Air Force, has been named by several sources -- including Eugene Hasenfus, the surviving crew member of the downed C-123 cargo plane -- as a major transshipment point for privately operated flights allegedly carrying arms and supplies to the rebels.

Concern over possibly illegal US ties to the supply operation has been heightened by these recent developments:

Documents recovered from the downed cargo plane indicate that the resupply operation, manned entirely by Americans, made extensive use of military airfields in Honduras constructed by US forces during maneuvers in 1984. US officials have said the airfields would not be used to support the contra war.

Two men with past and possibly present CIA connections have been named by Mr. Hasenfus as overseers of rebel resupply flights operating out of the Ilopango base.

Both Vice-President George Bush and his national-security aide, Donald Gregg, had contact with one of the two men, Max G'omez, and may have played key roles in organizing a network of private military and financial support for the contras. Mr. Bush's office has denied the latter charge.

The business card of a State Department contractor reported to have close ties to the National Security Council was found on the body of one of the two Americans killed in the plane crash. The contractor, Robert Owen, is said to be the principal conduit between NSC official Oliver North and contra groups.

Meanwhile, a report released last week by Sen. John Kerry (D) of Massachusetts says funds raised in the US to provide humanitarian aid to the contras may have been used to pay for mercenaries, military training, and weapons, in violation of US neutrality and arms export laws.

The report also says US officials may have sustained such efforts by helping raise funds from the private sector and by providing direct military advice to contra commanders long after Congress in October 1984 barred US officials from ``directly or indirectly'' aiding the contras.

``Either US officials have lied to the American people and violated the restrictions passed by Congress, or private citizens have, with apparent impunity, violated US laws designed to prevent private citizens from carrying out unauthorized weapons trafficking or military adventures abroad,'' says the report, based on interviews with 50 unnamed sources.

US officials say they strongly support private efforts to sustain the contra war but have denied any US government connection with the supply operation.

``We are barred from doing that, and we are not doing it,'' Assistant Secretary of State Elliott Abrams said last week in a television interview. ``This is not in any sense a US government operation.''

But various experts familiar with US military and intelligence operations in the region say private groups ferrying supplies to the contras would almost certainly need US help to secure Salvadorean permission to use the base at Ilopango.

``Not just anybody can take off from Miami and land [at Ilopango] without the intercession of the US Embassy, the [US] Military Group, or members of the `spook group,' '' says Ed King, referring to Americans in civilian clothes at the base who are believed to be CIA employees.

Also, once a plane lands at Ilopango, US employees at the base would have to be used for flight planning, maintenance, and loading and unloading. Alternatively, US officials would have to ask Salvadoreans at the base to do the work.

Either way, King says, the US would be involved not just as an observer of the contra resupply operation but, at least in a limited way, in an actual operational role. The 1986 Intelligence Authorization Act bars US agencies, including the CIA and the Defense Department, from participating in ``logistical activities'' integral to contra military operations.

A House judiciary subcommittee says it will ask Attorney General Edwin Meese III to investigate the US role in abetting the contra supply operation.

Meanwhile, Senate Foreign Relations Committee staff will take depositions from at least 15 people in connection with the downed cargo planes.

Senate Republicans, skeptical of the authenticity of Kerry's findings and wary of looking too closely at events that could embarrass the Reagan administration, say they are reluctant to use the committee to launch a Watergate-style probe.