The United States is studying a new Angolan proposal in the latest round of negotiations aimed at ending the Cuban military presence in the southern African country.

State Department officials refused yesterday to divulge the contents of the proposal, saying only that further clarification would be sought from Angola. The proposal, received last week, is the latest move in negotiations begun six years ago and follows fruitless talks in the Angolan capital of Luanda last month.

Negotiations were resumed in mid-July after talks broke down last year when the Reagan administration began providing sophisticated Stinger antiaircraft missiles and other arms to rebel forces opposing the Marxist Angolan government. The Luanda discussions between Assistant Secretary of State Chester A. Crocker and an Angolan negotiating team were called a failure after the Angolans reformulated old proposals of a partial Cuban withdrawal, already rejected by the United States.

After talks in Havana last week, Angolan President Eduardo dos Santos and his Cuban counterpart, President Fidel Castro, issued a communique in which they pledged greater flexibility on the Cuban troops issue.

The State Department responded by asking for definite proposals.

The United States has had no diplomatic relations with Angola since its independence from Portugal in 1974. The administration has said Angola must first send home the estimated 37,000 Cuban troops and advisers stationed there and used primarily in the civil war with the UNITA rebels.

Withdrawal of Cuban troops is linked to the independence of neighboring Namibia, administered by South Africa.