To help ease a financial squeeze, the World Bank announced yesterday that it will impose a one-time fee of 1 1/2 percent on the face value of all new loans, in addition to interest rates, which currently are 11.6 percent. The charge is necessary, a bank spokesman said, to "send a signal to the markets that the Bank is and intends to continue to be a sound institution."

"Adverse" impacts arising from higher interest charges and foreign exchange costs caused the bank to take steps that would maintain its top credit rating in the markets, the spokesman said.

Under the new rate plan, a borrower has the option of paying the fee "up front" or adding it to the rest of the loan. The new fee is in addition to the existing "commitment fee" of 3/4 percent on World Bank loans prior to actual disbursement.

At the same time, the bank's soft-loan affiliate, the International Development Association, moved to cover more of the costs it incurs in making its interest-free, 50-year loans to the poorest of its member countries.

Presently, IDA charges a 3/4 percent fee on the disbursed portion of its credits. Contrary to a published report, that will remain unchanged. But now IDA also will charge 1/2 percent on the undisbursed portion of credit as soon as the funds are committed. In the past two years, IDA has lost money.

These added charges reflect a new mood of austerity at the bank and IDA. The United States, the biggest contributor over the years, has been trying to cut back its proportional share. Under the Reagan administration, funds pledged to IDA have been stretched out, leading to the prospect, according to World Bank President A.W. Clausen, that the character of the IDA lending system will soon have to undergo a major alteration.

According to recently published reports, the U.S. Treasury will publish a recommendation on Jan. 20 that the U.S. annual contribution to IDA be reduced to $750 million a year by 1983. IDA is scheduled to average close to $1.1 billion for the three fiscal years ending 1983 if Congress passes the necessary appropriation bills.