Tests have shown the controversial Bigeye nerve gas chemical bomb, whose production President Reagan certified earlier this year as being in the national interest, to be unreliable, the Pentagon said Monday.

"Interim results indicate that the Bigeye is not operationally suitable," said John Krings, the Pentagon's director of operational test and evaluation said in his office's annual report to Congress.President Reagan certified Jan. 19 that Bigeye production was in the national interest. Congress required the certification because its watchdog agency, the General Accounting Office, in 1986 said the aircraft-dropped bomb was so flawed that it should not be produced.

A Pentagon official, who commented on condition of anonymity, said the term "not operationally suitable" meant the Bigeye had not shown sufficient reliability in tests of 58 prototypes last year.

"The problems seem to be minor, but there are too many of them," the official said.

A determination of whether or not the bomb is reliable enough will have to wait until 1990 when a sufficient number of production model Bigeyes will be available, the official said.

"There aren't any more prototypes, and there isn't any money to build more,"said the official.

In February, the Pentagon said full-scale production would not begin until 1990, with only limited production until then. It awarded a $48 million contract to Combustion Engineering Inc. of Bloomfield, N.J., to build a production facility at Pine Bluff Arsenal, Ark.

The Bigeye is one of a new class of chemical weapons called binary munitions, whose harmless chemicals do not become lethal until mixed during flight to the target.