Defense Secretary Caspar W. Weinberger has refused so far to support land basing for the new MX intercontinental missile, and his position has deepened the rift between him and defense hardliners within the Reagan administration and in Congress.

Weinberger has said his concern about the system, which would scatter some 200 MX missiles among 4,600 concrete shelters in Nevada and Utah, is partly that expected environmental lawsuits could delay deployment beyond 1986.

Weinberger's latest action, to appoint a panel of non-government experts to review deployment of the MX missile, was drawing fire from his critics yesterday; they fear the committee will give the basing system only mixed reviews.

The panel, to be chaired by Dr. Charles H. Townes, a Nobel Prize winner now at the University of California at Berkeley, is to report to Weinberger before June 1, the date on which the MX basing decision is now scheduled to be made.

Although Weinberger characterized the group in a television interview Wednesday as having "impeccable credentials," a top-ranking military man noted that one of those on the list, Dr. Wolfgang K. H. Panofsky, had led the opposition in 1969 to the ABM, and now advocates putting the MX out to sea in a submarine.

Another source within the Reagan White House said that the panel "was bound to come in with some dissenting views" on the controversial land-basing system for the MX, making it even more difficult to sell to the public.

Still another administration source indicated the Secretary of State Alexander M. Haig Jr. may be applying pressure to have the MX decision made in favor of the currently approved basing plan.

Haig, according to this source, told his colleagues at a recent National Security Council meeting that the European NATO members were watching how the Reagan team reacted to opposition to the MX basing because there is political pressure in their countries against the current plan to put new medium-range missiles in England, West Germany and Italy. A Capitol Hill source pointed out that Weinberger, at a closed-door session of the House Armed Services Committee Tuesday, refused to give his support to a basic principle of the defense establishment: the need for a land-based ICBM system that could not be destroyed by a Soviet first strike.

He "would not commit to a land-based, survivable missile system," according to this source, even when pressed by Rep. Robin Beard (R-Tenn.), one of the leading congressional advocates of a stronger defense.

Weinberger has made it clear that he is in favor of building the MX missile, which will carry 10 separate hydrogen bombs, each with explosive power equivalent to 335 kilotons, or 335,000 tons, of TNT.

Because of the size of the MX, it cannot be fitted on any U.S. submarine now being built. Weinberger flirted briefly after taking office with the idea of putting the missile on surface ships, but reportedly was talked out of that by both Air Force and Navy officers who pointed out how vulnerable to attack the ships would be.

Pentagon officials and defense experts who have been studying the problem of basing the new missile for almost 10 years, point to the decision of the Carter administration, which was not considered hardline on defense, as was proof that the present multishelter plan, costly as it may be, is the only way of assuring an ICBM that could survive, and thus deter, a first strike by Soviet missiles.

One Pentagon source said the military services have begun pointing out that Weinberger's fear of environmentalist lawsuits on the MX is ironic, "given that this is the same administration that has approved drilling for oil off the Santa Barbara coast and moving against regulations, particularly in the environmental field."