The Carter administration yesterday stressed that the first agreement in 16 years for the exchange of any diplomats between the United States and Cuba is a limited "step forward."

Under the new accord with President Fidel Castro's government, about 10 Cubans in a few months will return to the former Cuban embassy on upper 16th Street, NW, operating under the flag of Czechoslovakia.

The official identification for the two buildings will be "Embassy of Czechoslovakia in Washington - Cuban Interests Section." An equal number of middle-level diplomats and secretaries will move into the former U.S. embassy on Havan's once-fashionable waterfront. The sign there will say: "Embassy of Switzerland in Havana - U.S. Interests Section."

Cuba also notified the State Department yesterday, officials said, that it plans to release "immediately" 10 American jailed in Cuba on narcotic charges, and to review the cases of other imprisoned Americans.

State Department spokesman John H. Trattner said that action "can be taken as a gesture," but he asked for "compassionate consideretion" of 20 other remaining Americans, especially elderly persons held for years on political grounds. Officials later said eight of the 20 Americans in Cuban jails are political prisoners.

White House press secretary Jody Powell cautioned reporters about "getting too carried away" about the agreement to open diplomatic interest sections.

Powell cited President Carter's recent reference to "these first faltering steps" toward restoring relations, which the United States severed with the Communist government on Jan. 3, 1961.

This can be viewed, Powell said, "as a step - primarily a procedural step - that will make it less difficult to have discussions that hopefully can resolve the substantial differences that still exist between this country and Cuba."

Although domestic opposition to normalizing relations with Cuba has diminished from earlier years, the subject is still controversial.

Sen. Bob Dole (R-Kan) served notice yesterday that he will introduce a resolution next week to seek firm conditions for diplomatic recognition of Cuba and relaxing the U.S. trade embargo.

"Castro has made no concessions to us," Dole said in a statement, "yet the President seems intent upon sending an American ambassador to the island before the year is out."

Dole said "our bargainign chips" with Castro should include payment of $2 billion for U.S! property confiscated after Castro seized power in 1959: release of all American political prisoners; withdrawal of all Cuban forces and advisers from Africa; Cuban renewal of the antihijacking agreement which expired in April, and assured security of the U.S. naval base at Guantanamo Bay.

The State Department's announcement yesterday of the partial accord, a day after Havana's, said under notes exchanged in New York City on May 30:

"This agreement will facilitate communications between the two governments and will provide a greater range of consular services for the citizens of the two countries than are currently available."

Spokesman Trattner said the senior diplomat in each nation's interest section will hold the rank of councilor, the third rank below ambassador and minister.Interest sections can perform much of the same work as an embassy, without the protocol, although U.S. officials are not stressing that.

The sections will be opened in "two or three months," Trattner said. The interval will be required to prepare the buildings and living quarters. An American survey team will be sent to Havana, where the former U.S. embassy, once among the largest in Latin America, is in poor condition, its roof leaking.

Cuba's two buildings here, the main one at 2630 16th St. NW, are in better condition. The Czechoslovak embassy has been using the former embassy for housing, and a building across 16th Street for a diplomatic community school.

Powell said at the White House that the continued presence of Cuban troops in Angola is among the largest obstacles to restoring diplomatic relations.

Only a week ago State spokesman Trattner cautioned that any major expansion of new Cuban military personnel in Ethiopia, now reported to number 50 technicians, could jeopardize improved relations with Havana. President Carter in February emphasized U.S. concern about human rights in Cuba, and the Cuban troops in Angola, which by U.S. estimate still number 10,000 to 15,000.

However, former Secretary of State Henry A. Kissinger, who authorized secret talks with Cuba in 1974-75, made withdrawal of Cuban troops from Africa a precondition for better relations. For years the United States also had said Cuba must abandon "the export of revolution" in this hemisphere.

Rep. Ronald V. Dellums (D-Calif.) said Castro told him last week in Cuba that Cuba plans to increase its personnel in Ethiopia to 311, but all will be doctors or medical technicians.

After briefing the President on his talk with Castro, Dellums said, "I believe that if the Cuban forces had not been in southern Africa [Angola], South Africa would have marched all the way north."

The Carter administration made several overtures to Cuba, including the removal of restrictions on American travel to Cuba. A breakthrough came in the recent U.S. Cuban agreement on fishing rights, and the visit of the first American official to Cuba since 1961.

Cuba's major concern is removal of the U.S. trade embargo, a larger obstacle to normalization than memories of the American-supported Bay of Pigs landing in 1961 to try to topple Castro or covert plans to assassinate him. U.S. officials estimate it costs the Soviet Union about $3 million a day in aid or subsidies to support the Castro government.