Zairian President Mobutu Sese Seko said yesterday that his government is prepared to renew diplomatic relations with Israel "immediately" but will take no action until other black African nations take a stand.

Spending the final day of a "working visit" to Washington, Mobutu told a news conference that he broke Zaire's ties with Israel in 1973 in a show of support for Egypt and its lost terroritory.

But now that Egypt has resumed relations with Israel, and the last of occupied Egyptian terroritory is scheduled to be returned in April, the Zairian strongman said the resumption of relations is "not a difficult problem" for his country.

"As far as we're concerned, we could do it immediately," Mobutu said.

"But Zaire is not alone in Africa. There must be consultation with other African countries . . . . For the time being, I will wait to see what the other ones are going to do."

Israel stands in diplomatic isolation from many Third World countries that support Palestinian self-determination.

Mobutu also told reporters that he is increasing his country's contribution to the Organization of African Unity's peace-keeping force in Chad from 800 troops to 2,000.

He said Guinea, Togo and Benin are facing problems that have delayed them from meeting their commitments so "I decided to increase my troops there."

The only other nations contributing to the OAU force are Senegal and Nigeria, Mobutu said. He added that the U.S. government has agreed to supply equipment and material "by the end of the week."

Mobutu, who heads one of Africa's most strategically located and mineral-rich countries, said he received "full satisfaction" from President Reagan and other high-ranking U.S. officials this week in his quest for more economic and military aid.

But he steadfastly avoided describing the requests he made and any commitments he got in dollar terms.

The State Department said at the outset of Mobutu's visit this week that total U.S. aid for Zaire in fiscal 1981 was almost $31 million, including $24 million for food and developmental assistance and the rest for military aid.

Officials said the Reagan administration was requesting $45.5 million, including $33.5 million for food and developmental assistance, for fiscal 1982.