Nigeria, black Africa's major oil exporting nation, has sent warning signals to the United States and Britain that it will retaliate if they recognize the new black-led government under Bishop Abel Muzorewa in Rhodesia.

The signals are regarded as significant since Nigeria now is the second-ranking exporter of oil to the United States, a role that is given added weight as a result of gasoline shortages.

The United States currently imports approximately 1 million barrels of oil daily from Nigeria, or about 15 percent of its total imports, at a cost in excess of $5 billion yearly.

Although the Nigerians have not yet specifically threatened an oil embargo, they sent a statement to all embassies here in Lusaka early this month assuring African and Western nations that they will make an "appropriate response" to any American or British steps toward recognition.

In addition, they have told U.S. Embassy officials in Lagos privately that this response may be far stronger than Washington now anticipates, according to diplomatic sources here.

Nigeria already has given a bite to its warning by exluding British companies last week from bidding on a $200 million port construction contract despite a British loan for the project. It also told the British they may be shut out from all federal government contracts if Margaret Thatcher's new conservative government recognizes the Muzorewa government, according to British commercial and diplomatic sources here.

The Nigerian action reportedly has sent British officials scurrying to reassure Lagors that London has no intention of "rushing" to recognize the Muzorewa government.

But the Nigerian have made their point, namely that they are serious in their stated intention of using their economic weight to halt what one British newspaper has called "creeping Western recognition" of the black-led government in Zimbabwe-Rhodesia.

Nigerian Civilian and military leaders are reported to be discussing such retaliatory measures as nationalization of British or American companies, an oil embargo, withdrawal from the British Commonwealth and ban on British and American companies bidding on Nigerian contracts.

U.S. investments in Nigeria amount to about $1.2 billion, most of it in the oil and gas industry, according to the U.S. Embassy in Lagos.

In addition, Nigeria slowly has been displacing South Africa as the biggest market for U.S. goods in sub-Sahara Africa. In 1977, U.S. exports to Nigeria were just under $1 billion while those to South Africa slightly above.

While figures for 1978 were not available here, it seems likely Nigerian has surged ahead by now given the upward trend in economic trading between the two countries.

Nigeria is coming under increasing pressure from the so called front-line states involved in the Rhodesia conflict to use its economic influence with Washington and London as a last resort to halt Western moves toward recognition. These states are holding fast in their support for the Patriotic Front, the alliance of black nationalist guerrillas seeking to overthrow the Muzorewa government.

Presently, the five front-line leaders are trying to arrange a summit meeting that would include both Nigeria and Ethiopia to draw up a concrete military and political plan to counter the new black-led Zimbabwe-Rhodesia government. This would presumably include economic retaliation from Nigeria and Ethiopia for the guerrillas and their front-line backers.

Western observers here are still uncertain just how far Nigeria is willing to go in using its economic weight with either London or Washington. It has never shown much interest in an oil embargo before, although it has made known its special concern for the wars of liberation being fought by black nationalists against the white-dominated governments of south Africa.

A 1977 attempt to punish the British-owned Barclays Bank for its investments in South Africa by throwing it out of Nigeria backfired and ended in hurting Nigerian interests more than British ones.

The nigerian government has made it clear it does not regard the Muzorewa government as legitimate. The Nigerian chief of state, Gen. Olusegun Obasanjo, said Friday that Nigeria regarded the April elections in Rhodesia as "mockery of democracy" and had no intention of recognizing the results.

Meanwhile, the government-owned Daily Times has warned in an editorial that the Carter administration would be making a "serious mistake" if it decided to build its relations with black Africa on the "political fraud" being perpetrated today in Zimbabwe-Rhodesia. Other Nigerian newspapers have said Washington's credibility in black Africa would be badly shaken and Nigeria would be obliged to take action against it.