The Reagan administration is withholding a $75 million U.S. contribution to the World Bank's special fund for Africa to see if it will be cut under the new deficit-reduction law, a Treasury official said yesterday. The contribution, approved by Congress Dec. 19, was to have been paid to the World Bank by the end of 1985. The bank, owned by 149 governments, is the biggest single source of aid for poor countries seeking new investments to raise their standard of living. The U.S. government owns the most shares in the bank.

The Treasury official, who spoke on condition his name not be used, said the $75 million for the World Bank will be delayed until March 1 to see if it will be cut under the Gramm-Rudman deficit-reduction law.

Edwin L. Dale, spokesman for the Office of Management and Budget, said in a telephone interview that the funds could be released earlier, and that, at most, $3 million would be held back. He said he did not know if the U.S. Treasury would pay interest to compensate the bank for money it might have earned if it had the $75 million in hand -- which for the two months could be an additional $1 million at current interest rates.