Significant concessions have been made by the major Southwest Africa (Namibia) liberation movement that appear to increase settlement with South Africa, it was learned here today.

As a result of the concessions, U.N. Secretary General Kurt Waldheim, who had long been reluctant to take such a step, has reportedly agreed to make contingency plans for a U.N. administrative presence in the territory during the transition period.

The concessions were made earlier this month in a three-day meeting in New York between Sam Nujoma, leader of the South West Africa People's Organization (SWAPO), and representatives of the so-called Western contact group - the United States, Britain, Canada, France and West Germany.

SWAPO, according to information that surfaced at the U.N. sponsored anti-apartheid conference here, agreed to accept a South African as administrator general of the territory during the transition period preceding full independence and agreed to accept the principle of elections for a Parliament.

Previously, SWAPO had insisted that the interim administrator general be named by the United Nations rather than South Africa. It had also opposed early elections for a Parliament, contending that rule of the territory should pass directly from South Africa to SWAPO since the United Nations has recognized SWAPO as the only legitimate representative of Namibia's 800,000 residents.

South Africa has administered the former German colony under a 1920 League of Nations mandate that was later revoked by the United Nations. South Africa has defied U.N. demands that it withdraw.

The South African government has agreed to eventual independence for Namibia, but hopes to pass control of it to an administration friendlier than the militant SWAPO.

The new SWAPO positions were passed on to the South African government last Friday. The next stage in the indirect negotiations is expected in the coming weeks in the framework of the Angle-American initiative on southern Africa.

The U.N. presence Waldheim has reportedly agreed to make plans for is understood to be administrative officials who would work in conjunction with the South Africa-appointed administrator general. Whether U.N. peacekeeping forces would be used in Namibia is a separate issue that reportedly has not been resolved.

The present compromise calls for establishing overlapping responsibilities between the South African administrator general, who is to take office Sept. 1 with SWAPO approval, and the U.N. special representative. The two officials are to work in conjunction with each other.

While SWAPO accepted the principle of elections for a constituent assembly, there has yet to be an agreement on the election machinery.

Despite the concessions, major differences remain. For example there is still dispute over whether final authority on election procedures would be vested in the U.N. special representative or the administrator general.

SWAPO reportedly insists that the U.N. representative "approve" all decisions while South Africa's version states that the U.N. representative be "satisfied" by the administrator's proposals.

It was also learned that a great deal of work remains on three major problems:

Withdrawal of South African troops, SWAPO wants the South African military out of Namibia in three to four months. South Africa hopes to keep a military presence as long as possible.

Supervision of a cease fire. Whether there should be a U.N. force to supervise the transition, has not been resolved.

Timing of any pre-election transition. South Africa wants the shortest possible transition period to give the advantage to candidates favorable to it. SWAPO wants the longest possible transition period because many of its members are abroad and would need time to establish themselves. Even those Namibia are restricted in their activities by the South African administration, and SWAPO feels that it needs time to organize.

South Africa officially has proposed Dec. 1978 for elections, but SWAPO probably would want a later date.

Walvis Bay, the only deep-water port along the Namibian coast, is a South African enclave used by its naval vessels and is said to "lurk in the background" as a major obstacle. In the New York talks SWAPO reportedly did not specifically mention the problem, but did insist on Namibia's "territorial integrity."

Observers speculated that South Africa might relinquish its claims to Walvis Bay, based on prior British sovereignty even during Namibia's German colonial period, in exchange for a Namibian government mindful of South Africa's interests.