The British-sponsored constitutional conference on Zimbabwe-Rhodesia that opened here today is the ninth major international attempt to solve the contentious, 14-year-old Rhodesian issue.

The first three efforts following former prime minister Ian Smith's unilateral declaration of independence from Britain in 1965 simply involved negotiations between the Rhodesian government and Britain, the colonial power.

Since then a variety of African parties have been involved and the last two abortive efforts, led the 1976 Geneva conference and the 1977 Anglo-American plan, have been mainly the result of joint efforts by the United States and Britain.

Over the years, six different British governments have sought to negotiate on the basis of six principles, which boiled down to a cumbersome journalistic acronymn, NIBMAR, standing for No Independence Before Majority African Rule.

Smith, who had declared there would be no black rule in 1,000 years, accepted the principle of African majority rule in 1976 under pressure from the U.S. secretary of state Henry Kissinger, aided by South Africa.

The key international negotiating phases:

1966 -- Smith and British Labor prime minister Harold Wilson meet on board HMS Tiger in the Mediterranean Sea and tenatively agree to a draft proposal suspending declaration of independence while a new constitution is drawn up. The Rhodesian Cabinet rejects the proposal.

1968 -- Talks between Smith and Wilson on HMS Fearless, anchored at Gibraltar, end after four days without agreement.

1971-72 -- Smith and the Conservative government of prime minister Edward Heath agree on a complicated plan that could produce an African majority Parliament but possibly not until well into the 21st century. The plans calls for approval by Africans and in a test of opinion carried out by a commission headed by Lord Pearce in early 1972, the Africans overwhelmingly reject the settlement to the surprise of both governments,

1974 -- The rejection leads to an upsurge of Africian political activity and a profusion of parties. Talks are held involving African nationalist movements, the Smith government and leaders of Tanzania, Zambia and Botswana. The talks, in Lusaka break down early in 1975 over terms of a cease-fire in the guerilla war that started in 1972 and release of poltical prisoners.

1975 -- Constitutional talks are held on a train spanning the Rhodesia-Zambia border on Victoria Falls bridge. The talks, involving Smith, South African prime minister John Vorster and Zambian President Kenneth Kaunda, along with Rhodesian nationalist groups, break down.

1975-76 -- Smith and guerrilla leader Joshua Nkomo hold a series of talks that break down over the timing of majority rule, extent of franchise and composition of an interim government.

1976 -- Kissinger launches a six-month diplomatic initiative to reach a settlement, including two trips to Africa. It culminates in Smith's agreement on the principle of majority rule and scheduling of a Geneva conference. It bogs down over details of an interim government.

1977-78 -- The Carter administration and the British Labor government of prime minister James Callaghan present an Anglo-American settlement plan that includes a detailed constitution plans for a transitional administration led by Britain, establishment of a combined military force and supervision by a U.N. peace-keeping force. Agreement is never reached on holding an all-party conference to approve the plan.

1979 -- The new Conservative prime minister, Margaret Thatcher calls the constitutional conference starting Monday that is to seek a settlement based on proposals approved by the Commonwealth conference in Lusaka in August.