Jerusalem — Zaire's resumption of diplomatic relations with Israel has been hailed as a breakthough by Israeli officials. Israel has been trying for almost a decade to shift Jerusalem's relationship with black Africa from a semi-clandestine status back to open diplomatic ties.
Israel's Foreign Ministry says it expects other African countries to follow Zaire's move in the near future. The completion of Israel's pullback from Sinai is seen as the catalyst for this diplomatic revival.
Twenty-five African countries severed relations with Israel in 1973 under Arab pressure. Most cited as the reason Israel's occupation of ''African territory'' -- the narrow strip east of the Suez Canal captured from Egypt in the Arab-Israeli war of 1973. Almost all of the 250 Israeli experts providing technical assistance to African countries were also forced to leave.
However, Israel's commercial contacts with black Africa managed to survive, becoming a conduit through which Israeli influence was able to grow despite the absence of official relations.
There are today more than 4,000 Israelis working in 17 black African countries, and Israeli exports have grown from $30 million to these countries in 1973 to more than $100 million today.
Despite this thriving economic relationship, Israel has long been anxious to reestablish diplomatic ties. ''The Arabs try to isolate us, to make us pariahs of the international community,'' says an Israeli official. ''We're trying to break out of this circle of isolation.''
Israel has for some time had resident Israeli interest sections operating out of other nations' embassies in Zaire, Kenya, Ghana, the Ivory Coast, and Gabon. There are also nonresident interest sections in several other countries. There are some 500 Israeli families in Nigeria despite that country's large Muslim population.
African countries have been interested in Israeli involvement because of the level of expertise Israel has been able to provide in agriculture, water resource development, and other areas free from the taint of ''imperialism'' often associated with big power involvement.
Some Israeli political observers not connected with the government are less certain than Foreign Ministry officials that Zaire's move will be followed by other African states.
''It's still not clear whether Zaire represents a trend or a special case,'' said a Hebrew University authority on Africa.
According to Israeli press reports, Zaire asked Israel to intervene with Washington in order to win greater economic assistance for Kinshasa, Zaire's capital. Before relations were severed in 1973, Israel conducted training programs for Zaire forces. Zaire's President Mobutu Sese Seko graduated from parachute jump school in Israel.
A visit by Israeli Defense Minister Ariel Sharon to Zaire last November is regarded as a turning point in Israel's diplomatic campaign. The minister spent two days with Mobutu, some of it on a cruise boat on the Congo River. Israeli sources say the theme of their talks was the threat of Soviet expansionism to Africa and the Middle East.
Mobutu agreed to resumption of relations but only after Israel completes its withdrawal from Sinai. The withdrawal was completed last month.
Prime Minister Menachem Begin has accepted an invitation from Mobutu to visit Zaire and said he will probably go in the fall after his injured leg heals.
Meanwhile Jerusalem has also been cheered by the decision of Costa Rica to move its embassy back from Tel Aviv to Jerusalem.