Senate Majority Leader Robert C. Byrd (D-W. Va) said yesterday he has warned President Carter that the B-1 bomber could cost $100 billion over the next 25 to 30 years - or, as Byrd put it, "$100 for every minute since Jesus Christ was born."

Byrd told reporters he laid out his objections to full-scale production of the controversial replacement for the B-52 in a letter to the President Friday, in which he urged what he called a "go-slow" approach to the B-1.

Carter opposed the B-1 during the campaign as "wasteful" but has shown signs of reversing himself since the election. He is expected to decide this week whether to put the new bomber into full production and, if so, on what scale.

The Air Force has requested construction of 244-B-1s, at a cost of more than $100 million per plane, making it the most expensive combat plane ever built.

Byrd said he would not, object to funding five of the bombers, as proposed in a military appropriations bill now before Congress as a way of "keeping the way open for increasing technology in this field."

But to embark on full-scale production would "lock us out of military alternatives that are less costly and less vulnerable" to enemy assault, as well as soak up money needed for domestic programs, Byrd said.

Byrd said his analysis, based on Pentagon and other information, put most of which will last 10 years or 25-to-30 year life at $100 billion, which, he said, is too much to "gamble" on a single piece of military hardware.

The United States has 400 B-52s, more, and can be equipped with the price tag of the B-1 fleet over its cruise missiles, Byrd said.

Aasked about the value of the B-1 as a bargaining chip for strategic arms limitations talks with the Soviet Union, Byrd said the Russians fear the cruise missile more than the B-1. And so long as the United States has the techonology to build a B-1, the bomber can be a factor in arms negotiations, he said.