Several senior senators challenged President Carter's defense yesterday across abroad from extending from arms sales abroad to the MX Block-buster missile.

Senate Majority Leader Robert C. Byrd (D-W.Va.) called for a moratorium on arms sales to Iran after complaining that the administration has failed to implement a cohesive weapon export policy in concert with Congress.

Sen. William Proxmire (D-Wis.) warned that there is so much confusion over Carter's manned-bomber policy that the President's decision to cancel the B-1 may be "overturned by a subtle turn of events.

Sen Edward M. Kennedy (D-Mass.) said U.S. cruise missiles based on land on ships - as distinguished from aircraft - threaten to blow up chances of a U.S. Soviet arms control agreement.

And Sen. Thomas J. McIntyre (D-N.H.), chairman of the Senate Armed Services Research Subcommittee, termed Defense Secretary Harold Brown's tentative decision to go ahead with MX intercontinental missile "a disastrous mistake."

Byrd, in a floor speech early in the Senate's long day, said the United States already has sold Iran $17 billion worth of arms since 1972, a figure that would rise to $18.2 billion if the proposed sale of the Airborne warning and control system (AWACS) goes through.

"This is an astounding amount of military equipment to deliver to any country," Bryd said, and requires a growing number of Americans to work in Iran. "Any further would constitute an exception to sound and prudent United States policy."

No more arms should be sold to Iran, Bryd continued, until the Carter administration "has undertaken a thorough analysis not only of the need for more U.S. technicians in Iran, but of Iran's capacity to absord and utilize these major weapons systems."

While applauding Carter's pledges to bring arms exports under control, Bryd said Congress is still being asked to approve all kinds of weapons sales without the administration providing adequate justification for them.

He suggested that Congress consider increasing its authority over arms sales abroad by requiring the administration to get "explicit" congressional approval ahead of time. Currently, to stop an arms sales Congress must pass a resolution of disapproval.

The other challenges to Carter's military policies came last night when the Senate took up the bill to give the Pentagon an extra $364 million for fiscal 1978 to restructure its strategic forces in light of the President's decision to cancel the B-1 bomber.

Proxmire, in noting that the Senate Armed Services Committee had cut the Pentagon's request for $50 million to experiment with a wide-bodied transport as a cruise missile carrier, said bomber advocates have embarked on a strategy to "starve" that option to death.

If the Pentagon is prevented from building a plane to carry cruise missiles, Proxmire said, the administration then will have to build a new bomber. He said that $20 million in the supplemental money bill to explore the F-111 as a bomber is really part of a larger strategy to force that plane into production.

In a related action, Proxmire wrote a letter to Carter on Thursday urging him to speak out to clear up the confusion stemming from the Pentagon's expressed willingness to consider the F-111 as an alternative to the B-1 bomber.

Kennedy, in statements released yesterday, said he had grave concerns about the destablizing effects of the cruise missile when based on land or on ships, and on the MX nuclear blockbuster that the Air Force wants to build to replace the minuteman intercontinental missiles now deployed.

McIntypre, before joining Kennedy in a colloquy on the Senate floor, said in an interview that Brown's tentative decision to accelerate development of the MX by spending $245 million more on it in fiscal 1979 was a "disastrous mistake" from an arms control standpoint.