Sens. Richard G. Lugar (R-Ind.) and Edward M. Kennedy (D-Mass.) said yesterday that they will try to pass new sanctions against the white South African government as soon as possible. But Chester A. Crocker, the architect of the administration's Africa policy, said the United States wants to wait for British Prime Minister Margaret Thatcher to take the lead on tougher policies.

The Lugar and Kennedy statements on NBC News' "Meet the Press" apparently were an effort to pressure President Reagan to abandon his opposition to economic sanctions. The sanctions debate became intense after Reagan rejected sanctions in a Tuesday speech. However, under widespread criticism, Reagan on Thursday seemed to backtrack somewhat by saying "we haven't closed any doors" against sanctions. Lugar's statements indicate that some Senate Republicans who generally support the president are not satisfied.

Lugar, chairman of the Senate Foreign Relations Committee, predicted his sanctions proposal would pass by the two-thirds majority needed to override a presidential veto. He said he hopes the committee will have a bill "ready for the Senate floor" by Thursday.

Lugar called for withdrawing landing rights to South African planes, freezing South African bank accounts in the United States, forbidding new investment in South Africa, restricting U.S. visas for South African officials and banning exports from industries owned by the South African government.

"I have no indication that it would be acceptable to Reagan ," he said.

Kennedy, who has cosponsored a Senate proposal for stronger sanctions than those proposed by Lugar, said he supports "strong economic sanctions or disinvestment." The House has passed a proposal requiring total U.S. disinvestment from South Africa.

Crocker, assistant secretary of State for African affairs, said on CBS News' "Face the Nation" that the administration is waiting for the British to make decisions on their South Africa policy.

Like Reagan, Thatcher has been criticized for her stand against South African sanctions. She is expected to yield somewhat during a summit meeting of Commonwealth nations next weekend in London. "We don't want to cut directly across that the British meeting ," Crocker said.

Sen. Orrin G. Hatch (R-Utah) also said on "Face the Nation" that "Reagan has not done more than the Tuesday speech up till now" because "the leader in this area has to be Margaret Thatcher." Hatch added, "I think she's about ready to move."

Crocker and Hatch said Britain has a stronger historic connection to South Africa than the United States. South Africa was a member of the British Commonwealth until 1961.

British Foreign Minister Sir Geoffrey Howe is due to return this week from a mission to southern Africa, and Crocker will fly to Britain this week to confer with him, other British officials and representatives of other unspecified European countries.

A senior administration official also said in an interview Friday that the administration would prefer to postpone making a major change in its South Africa policy, to act "in tandem" with the international community, especially the British. However, he said strong pressure from Congress may force the administration to adopt sanctions before Britain acts.

Asked about a New York Times report that Reagan will renew a one-year ban on certain exports to South Africa, Crocker said, "if things don't improve, there's a very clear likelihood we would go in that direction."

The one-year ban on certain loans, sales of weapons and nuclear technology to the South African government, and sales of computer equipment to the South African police is due to expire at the end of August.

Bishop Desmond Tutu, a prominent antiapartheid spokesman in South Africa, gave his own proposal of Western measures against South Africa in an appearance on "Meet the Press."

Tutu called for "anything that would knock the bottom out of the confidence of the market" in South Africa.

He suggested that Western banks flood the market with gold, one of South Africa's major exports, that Western countries refuse to let South African Airways planes land and that all telecommunications with South Africa be cut until the government ends its state of emergency and releases political prisoners.