Guerrilla leader Joshua Nkomo announced yesterday he would halt military activities along the border between Zambia and Zimbabwe-Rhodesia to help assure the safety of 40 government leaders and Queen Elizabeth. who are expected to attend the British Commonwealth summit here in August.

At the same time, the black nationalist leader accused the white-supported government in Zimbabwe-Rhodesia of deliberately mounting "provocative attacks" on "refugee" camps around the Zambian capital during the past two weeks. He also charged the government of Bishop Abel Muzorewa with conducting a malicious anti-zambia campaign in a bid to force transfer of the conference elsewhere and the cancellation of the queen's trip.

Nkomo said here that in order to eliminate any pretext for a Zimbabwe-Rhodesian attack during the conference he would suspend military activitics along the border from July 25 through August 10. The conference is scheduled to run from August 1 through 8.

A spokesman for Nkomo told Washington Post foreign correspondent David B. Ottoway that the announcement meant that guerrillas of the Zimbabwe African People's Union [Zapu] would cases infiltration of Zimbabwe-Rhodesia, but that there would be no case-fire inside that country.

The nkomo spokesman also said that the two wings of the guerrilla alliance known as the Patriotic Front had established a joint military command following talks last week between Nkomo and Mozambique-based guerrilla leader Robert Mugabe This alliance means that ZAPU guerrillas would begin operating from Mozambique as well as Zambia, he said.

Meanwhile, a special U.S. envoy to Zimbabwe-Rhodesia, Jeffrey Davidow, began making contacts with government officals in Salisbury, as the start of establishing unofficial relations with the Muzorewa government. Muzorewa is scheduled to fly to the United States Sunday for talks with Secretary of State Cyrus Vance.