LONDON — PRIME Minister Margaret Thatcher says that after suffering the stick of sanctions, South Africa's white regime should be proffered the carrot of encouragement. She is determined to put her case to the world community - if necessary, with a stick in her hand. Almost alone among the 12 members of the European Community (EC) and the 49 members of the British Commonwealth, Mrs. Thatcher is campaigning to make the release of Nelson Mandela trigger the early lifting of economic sanctions against South Africa.
With typical determination, she has ordered British sanctions lifted immediately, and has dispatched letters to world leaders proposing that they follow London's lead.
At a meeting in Dublin of EC ministers on Feb. 20, Douglas Hurd, her foreign secretary, will formally propose an end to the community's sanctions program.
Despite Thatcher's persistence, the idea will almost certainly be rejected.
Prime Minister Charles Haughey, host for the Dublin meeting of the EC, said Feb. 12 that the time was ``not ripe'' for lifting sanctions - and he personally thought it would not be until South African President Frederik de Klerk agreed to repeal the Group Areas Act - segregation by law - and lift the South African state of emergency.
The Irish leader appeared to be reflecting the views of all EC countries, except Britain. A statement Feb. 10 by the European Commission, executive arm of the EC, welcomed the release of Mr. Mandela, but said further steps were needed - ``especially the lifting of the state of emergency.''
In the Commonwealth, which over the last 29 years has progressively tightened sanctions against South Africa, Thatcher's appeal for an early easing of the policy was met with a flat ``no.'' Sir Shrideth Ramphal, the Commonwealth secretary general, said: ``Mr. De Klerk has made a good beginning, but much more must be done before sanctions can be lifted.''
Within hours of De Klerk's speech on Feb. 2 announcing the imminent release of Mandela, Thatcher began signaling her firm conviction that it was time to abandon sanctions. She said British investment in the white-ruled republic, suspended under a voluntary ban, should be resumed.
The prime minister warmly praised De Klerk's ``brave and imaginative'' new policies and insisted that the time had arrived to ``reward his courageous decision to release Mr. Mandela.''
Neil Kinnock, leader of the opposition Labour Party, denounced the prime minister's action. He said slackening sanctions now would mean the apartheid regime had ``won a great prize for making the smallest change,'' and urged Mr. Haughey to ``do everything possible to sustain community pressure on Pretoria.''
The only other EC country to soften its South Africa line is the Netherlands, where parliament has postponed legislation that would have prevented Dutch companies from investing there.
EC sanctions against South Africa date from 1985. They include a ban on arms supplies and oil exports, an embargo on cooperation in nuclear energy, a ban on imports of South African iron and steel, and forbidding of new investment.
Sanctions applied by British Commonwealth countries closely parallel EC policies. In addition, the Commonwealth bans sporting contacts with South Africa.
In the past, Thatcher has often found herself in a minority of one in both the EC and the Commonwealth when these policies were decided.
Those, however, who believe there is still a need for the stick to be wielded include influential individuals and groups in South Africa. Among them is Mandela himself, who in Cape Town on Feb. 10, the day of his release, urged the world community to maintain sanctions.
The prime minister had planned to hold a press briefing after Mandela's speech, but when reports reached London that the black leader had called for the policy of armed struggle to be continued, she canceled the briefing.