Britain, the United States and other allies are thinking of calling on the U.N. Security Council to order Soviet and Cuban Military out of Angola and Ethiopia, a British government spokesman said yesterday.

Lord Goronwy-Roberts, a Foreign Office minister of state, emphasized that the Western powers are first awaiting the outcome of the peace initiative launched by the Organization of African Unity.

He said the allies were giving priority to the OAU effort because the African states have "a very strong and firms view" that they should take the lead.

In a dispute growing out of the fighting between Ethiopia and Somalibacked forces, Egypt seized two passenger airliners belonging to Kenya. The action was in retaliation for Kenya's forcing down an Egyptian cargo plane on Wednesday. Kenya's official news agency said that the Egyptir Boeing 707 had illegally entered kenyan air space with a shipment of arms for Somalia.

Later yesterday, the Egyptian Foreign Ministry announced that an agreement had been worked out with Kenya to exchange the three impounded planes.

Egypt had seized one of the Kenya Airways planes while it was making a regular stop at Cairo. The second was reportedly forced down by an Egyptian fighter plane.

Some of the 114 passenger aboard the two planes were put aboard planes of other airlines going to their destination. The remainder were put up at Cairo hotels.

The two countries are supporting opposing sides in the conflict between Ethiopia and Somalia, Egypt has said it would respond to Somalia's plea for military aid to counter the Ethiopia's offensive againt Somalia-back insurgents in the Ogaden region.

Somalia began running short of military supplies when the Soviet Union switched its support to the Marxist government in Ethiopia. Kenya, which rejects Somali claims on some of its territory, has been backing Ethiopia in the dispute.

In Washington, government sources said the Soviet passenger ship Rossiya landed Wednesday at the Ehiopian port of Assab after a voyage around Africa from Angola, where Cuba maintains more than 20,000 troops.

Sources said the Rossiya waited until after dark to let off its passengers and there was no estimate of how many or what sort of personnel it carried ried.

According to diplomatic sources in Addis Abba, Ethiopia's capital, an additional 1,500 Cuban troops will be brought to that country by the end of this month. The .S. State Department has eestablished that they are already 3,000 Cuban troops there, 2,000 of them in combat.