Presidential advisers may recommend a pocket veto of the bill ebill granting a $1.6 billion subsidy of the District of Columbia's unfunded pension programs because of the high cost, it has been reported.

The initial report came from David A. Ryan, president of the D.C. Fire Fighters Association, and was confirmed by one source in the Carter administration and by an aide to the chief Senate sponsor of the bill.

City officials and lawmakers have said that, without major federal support of the pension programs, the D.C. government may ultimately be forced into bankruptcy. The pension debt now exceeds $2.2 billion.

The subsidey bill won final congressional passage in the Senate just before the recent congressional adjournment. It would provide $85 million annually over the next 25 years - a total of $1.6 billion - to pay the already accrued cost of pensions mandated by Congress for D.C. police, firefighters, judges and school employes.

Other D.C. employes are covered by the U.S. civil service retirement program, to which the city and its employes make regular payments.

The original House version of the newly enacted bill called for a total federal subsidy of $769 million. At later hearings in the Senate, the White Houes's Office of Management and Budget (OMB) voiced support for a curtailed version that would have cost the U.S. Treasury about $480 million.

However, Sen. Thomas F. Eagleton (D-Mo.), the bill's chief Senate sponsor, and other members of the Senate Government Affairs Subcommittee that handles D.C. legislation, decided the federal government should, assume close to the full cost imposed by Congress before the city got home rule in 1975. That totaled at least $1.6 billion.

The bill also would curtail future disability retirements, the source of widespread abuses of the pensions system over the years.

Rayan, whose union supports the bill, said he heard that some OMB officials were prepared to recommend that President Carter kill the bill through a pocket veto - that is, by not signing it into law while Congress is out of session.

One administration source said that is a distinct possibility. Hadley Roff, top staff aide to Eagleton on D.C. matters, said "we're getting those vibes, too."

"We've been assured that no decision has been made, that the matter is under consideration," Roff said.

"Sure, the cost is high, but it will only be higher if it has to be dealt with in some future year," he added.

james Dyke, an aide to Vice President Mondale who headed the staff of the White House task force on D.C. problems last year, said the bill is being studied at a staff level in OMB, and no recommendation has yet been made.