The Pentagon conceded Tuesday that it doesn't have "a fully accurate picture" of the success of U.S. and allied air strikes against Iraq, and the chairman of the House Armed Services Committee said that was "causing heartburn" on Capitol Hill.

But Rep. Les Aspin, D-Wis., said he was still optimistic about the progress of Operation Desert Storm, "The evidence is, it's going extremely well," he said.He cautioned, however, that the successes of the opening days of the war were creating "such high expectations of what the rest of the war is likely to be, that we can't match them."

Pentagon spokesman Pete Williams said that there is not a huge gap between what the military is saying and what it knows about the damage.

"We don't have a fully accurate picture" about damage, Williams said on NBC's "Today" show.

Aspin, also appearing on the show, said, "We haven't got the specifics and that's causing heartburn in Congress, as well as it has in the press corps."

He said "the losses have been so low they may have set an unachievable standard for the rest of the war." He said it would have been realistic to expect loss of "somewhere in the range of 80-90 planes" at this point. "We've lost less than 20, not just the United States, but the whole allied coalition."

"Let me tell you that there's frustration level all over the building," Williams said. "It's not like election returns - you don't just go out and do this, and then the computer kicks it out the next day."

But Rep. Bill Alexander, D-Ark., says many apparent discrepancies could be resolved if the public had access to the same classified information House members received from the Defense Department. "I think there is an explanation," he said. "If it wasn't a classified briefing, I would give it to you," he told the Arkansas Gazette.

Alexander said the Pentagon has information about the fighting that could reassure Americans that the war is going well. "There is just no match," he said. "We are literally shooting ducks off the pond."

The Pentagon is anxious to avoid the credibility problems that arose during the Vietnam War, when the daily military briefing became known as the "5 o'clock follies."

Reporters are upset at the strict coverage guidelines imposed by the Pentagon in the gulf and by their inability to confirm any claims of U.S. success - partly because Iraq has expelled virtually all journalists.

"You have to remember that there has to be a balance between the amount of information that's released and the amount of information that we possess," said Lt. Gen. Tom Kelly, director of operations for the Joint Chiefs of Staff.