Portugal and its former colony Angola have reached an agreement on improving relations - a move that may lessen Angola's reliance on Cuban and Eastern European technicians, according to diplomats here.

In a three-day meeting early this week in the West African country of Guinea-Bissau, the presidents of the two countries agreed to name a joint commission to negotiate cooperation in several fields. Relations have been stormy since Angola won its independence from Portugal in November 1975.

The communique also said Angolans who fled to Portugal during the civil war that followed independence will be permitted to return.

Portuguese and U.S. sources here predicted that the agreements would lead to a resumption of trade and the return of as many as 7,000 Portuguese to Angola as contract workers.

At the same time the two presidents were meeting in Guinea-Bissau, U.S. Ambassador Donald McHenry was meeting with Angolan officials in Luanda in an effort to improve U.S. ties with Angola. The two countries do not have diplomatic relations.

President Carter had criticized the Cuban role in Angola and charged recently that Angola permitted rebels based there to attack neighbouring Zaire.

Angolan President Agostinho Neto was quoted yesterday in the Paris newspaper Le Monde as saying some of the Katangan rebels who invaded Zaire had come from Angola.

In the interview, Neto insisted that Angola had no prior knowledgw of the attack and that returning rebels had been disarmed. He said Angola had "no interest in fighting the Zairiana."

Observers here expressed the hope that the contacts with Portugal and the United States indicate Angola will be more open to Western nations and less dependent on aid and support from communist countries.

Renewed ties with Portugal are also expected to help the Angolan economy, badly hurt by the civil war that brought Neto's Popular Movement for the Liberation of Angola to power.

A recent visitor to Luanda said the Angolan capital, once a thriving colonial city was "almost like a ghost town." He said many stores were closed and those that were not had very little for sale.

The Angolan and Portuguese economies were so closely linked for centuries that a resumption of trade would be helpful to both countries, the sources said.

Angola could be a good market for many Portuguese manufactured goods that are not competitive in Europe.Portugal in turn could buy raw materials, including oil, from Angola.