The Reagan administration pledged $285 million today as part of a $470 million Western package to aid African refugees and said it was prepared to admit up to 8,300 to the United States through 1982 "if they want to come."

The U.S. commitment came on the first day of a two-day United Nations conference here on emergency aid for Africa's 5 million refugees, said to account for more than half the world refugee population.

Jeane Kirkpatrick, U.S. ambassador to the United Nations and head of the U.S. delegation to the refugee conference, told reporters that $126.5 million of the new U.S. aid package for 1981-82 would go to the Office of the U.N. High Commissioner for Refugees and the International Red Cross.

Of the remainder, $80.7 million would go for food aid, $65 million for resettlement of refugees in their countries of origin and $11.2 million to help relocate some of them in the United States. The Reagan administration was prepared to take 3,800 African refugees this year and another 4,500 in 1982, Kirkpatrick said.

In admitting the refugees, the Reagan administration would be acting on authority granted by Congress under legislation sponsored by the Carter administration, Kirkpatrick told reporters. The Carter administration never admitted any African refugees, however, she said.

Kirkpatrick told delegates to the 85-nation conference that "contrary to some reports, the government of the United States cares a great deal about our relations with the nations of Africa. . . . While deep cuts are being made in most domestic and foreign expenditures, the administration has recommended to the Congress a 30 percent increase in our overall aid for Africa -- the first real increase in African aid in a number of years."

Much of the increased U.S. aid to Africa is earmarked for Somalia and Kenya, which have agreed to give the United States access to military facilities as part of the American buildup in the Indian Ocean.

Kirkpatrick said the decision to increase aid to African refugees was due in part to the "many links" Americans have with Africa, particularly the 26 million Americans who trace their ancestral roots to Africa.

The large U.S. pledge appeared to bring the goal of the refugee conference -- $1.3 billion in new refugee aid spread over four to five years -- within the realm of possibility. Other pledges made today include $15.6 million in emergency aid to five African countries by the European Community, a $45 million pledge from West Germany, $19.6 million from Britain, $10 million from Denmark and a Dutch grant of $9.5 million.

The African refugee conference nearly failed to get off the ground, as Arab nations, led by Algeria, Libya and Syria, demanded the exclusion of Israel. Following a U.S. threat to leave the conference if Isreal were barred, a compromise was reached at the urging of African delegations permitting Israel to retain its seat as long as it does not take the rostrum. The Arab states agreed not to press the issue.