The State Department said yesterday that negotiations between Assistant Secretary of State Chester A. Crocker and Angolan officials this week produced "no breakthrough" on the U.S. demand that Cuban troops withdraw from Angola.

"The Angolan leadership does not yet appear to be united about how to proceed," department spokesman Charles E. Redman said of the talks, which took place in Luanda, the Angolan capital. "We are prepared to proceed with the diplomatic process when the Angolan side signals it has made the necessary decisions."

The United States has no diplomatic relations with Marxist Angola, and the Reagan administration has said it does not plan to establish any until the U.S.-estimated 37,000 Cuban troops and advisers go home.

While both sides indicated they were "pleased" with the resumption of talks after more than a year's break, no date was set for another meeting and U.S. officials were clearly disappointed with the result.

They said they had expected, on the basis of earlier Angolan assurances, a new Angolan proposal on the Cuban troop withdrawal issue that would revive prospects for negotiating a deal over this and the related question of independence for South African-administered Namibia. "What they had new to say was less than we thought," a U.S. official said.

A Luanda government statement said the talks took place Tuesday and Wednesday in "an atmosphere of relative cordiality and understanding." It said the two sides discussed Namibia and Angola's demand for a "complete and unconditional withdrawal" of South African troops from southern Angola but made no specific reference to the Cuban troop question.

In 1984, the United States rejected an Angolan plan to withdraw all but a few thousand Cuban troops, who would ostensibly be used to guard oil facilities in the north from rebel attacks. Since then, the number of Cuban troops has grown by several thousand.

The Senate voted yesterday to suspend for at least six months trade benefits enjoyed by Angola for oil exports to America. The amendment by Sen. Bob Graham (D-Fla.) was attached to the trade bill the Senate is expected to pass next week.