President Carter will commit himself to developing a new strategic bomber, perhaps as early as tonight when he accepts renomination at the Democratic National Convention, government sources said yesterday.

Such a commitment would steal a march on GOP standard-bearer Ronald Reagan and his adherents who have lambasted Carter for canceling the B1 bomber in 1977.

Breakthroughs in technology, sources said, will enable Carter to argue that his cancellation was a good move because the contemplated new bomber could foil Soviet defenses which are becoming lethal enough to down a B1.

One key breakthrough is a top-secret way to make a long-range bomber virtually invisible to enemy radar used to detect invading aircraft and aim guns and missiles at them.

Some Air Force enthusiasts have nicknamed this new bomber "Stealth" because of its ghost-like qualities. Technocrats explain Stealth presents a small, virtually undetectable "cross-section" to radar beams searching for it. They call it the High Technology Aircraft.

Presidential aides have drafted remarks about a new bomber for Carter to deliver to the convention tonight. But the president could decide to hold off. It depends in part on how he reads the mood of the convention, sources said.

"You're going to hear about these new bomber breakthroughs sooner or later in this campaign," one knowledgeable official said in discussing the administration's plan for combatting Reagan's claim that Carter has let down the nation's guard by canceling the B1 and other actions.

Although the Air Force is secretive about the breakthrough for foiling enemy radar, Lt. Gen. Kelly H. Burke, Air Force research chief, has said publicly that "high on our list of hardware explorations" in looking for a new bomber "is radar-absorbing material to reduce radar cross-section, which would improve survivability against both surface-to-air missiles and look-down, shoot-down" interceptor planes.

William J. Perry, Pentagon research chief, contends that Soviet strides in developing air borne radar that can look down and spot invading, low level bombers would doom the B1, which some members of Congress are still championing.

Perry also opposes the Strategic Air Commands's proposal to stretch the F111 into a long-range bomber for the 1980s and 1990s. "Over my dead body," Perry once said in asserting that the stretched F111 did not make sense. He would rather go for new technology to stay ahead of Soviet defenses.

Carter is thus in position to contend that the Pentagon experts agree that a better bomber than the B1 was worth waiting for. He does not have to commit himself to putting a bomber in production since that decision is years away.

Beside combating Reagan, Carter's commitment to a new bomber would get him off the hook with Congress. The House and Senate, in compromising on a weapons money bill this year, directed the Carter administration to choose some kind of bomber by next March 15.

For fear the Pentagon would balk at putting a new bomber in production, as it has for two decades now with the B70 and then the B1. Congress said it wanted whatever bomber was chosen to be in service by 1987.

Although this sounds like plenty of time to design and produce a new bomber, it actually is not. Modern warplanes take about 10 years to advance from the drawing board to the runway.

To some Air Force leaders, this means Carter will have to settle for a bomber simpler to build than the Stealth, perhaps leaving an opening for a variant of the B1. But they concede going back to any kind of bomber resembling the B1 would be politically uncomfortable for Carter.

An attractive middle ground for Carter would be to promise to develop a new bomber, give the public a peek at the wonder technology now in reach -- such as airplane skins which absorb or deflect radar beams -- and leave the specific choice open until after the November election.

The Air Force Scientific Advisory Board studied various bomber options last month and concluded that the new plane should be able to perform a multitude of missions, not just deliver a nuclear weapon to a stationary target. Missiles are accurate enough to do that, the board reasoned.

A multimission bomber could attack moving targets, drop mines or fire missiles at ships, the board concluded and reportedly discouraged the idea that a virtually "invisible" aircraft like Stealth could be built anytime soon.

Jimmy Carter would not be the first Democratic president to disclose warplane secrets to dramatize a commitment to a strong national defense. President Johnson on Feb. 29, 1964, ripped the secrecy veil off the A-11 spy plane built at the Lockheed "Skunk Works" in California, a highly secret facility that is expected to contribute technology to any new bomber deployed by the United States.