The International Monetary Fund said yesterday that U.S. banks and the lending institutions of other industrial nations gave $3 billion more to Third World countries than they got back during the first half of 1987.

The IMF, releasing figures for the first six months of the year, said "involuntary lending" to Mexico accounted for all of the difference.

In those six months, banks paid out $3.5 billion in "concerted" loans to Mexico, which already owed over $100 billion. Banks call that involuntary lending, since it is made only under pressure from the 151 governments that own the fund. The United States holds the largest block of votes.

In the same period last year, banks got back $7 billion more from the Third World than they lent.

In recent years, banks have been making few loans on their own initiative to heavily indebted countries, despite urgings by Treasury Secretary James A. Baker III and others.

The World Bank, the fund's sister organization, estimates Third World debt at more than $1 trillion. The IMF offered no new figure but said total debt rose in the first half of the year not only because of the new loans but also because Third World countries fell behind another $2 billion in payments of interest on old ones.

The fund's latest figures also show that Third World countries increased their deposits in banks by $18.5 billion the first half of 1987, in contrast to $18 billion in net withdrawals in the first half of 1986.

"Almost all of this increment reflected higher official foreign exchange reserves and came mainly from Taiwan ... and Mexico," said the fund's monthly "IMF Memorandum."

Taiwan has been accumulating dollar reserves in large part by heavy sales of its goods to the United States. U.S. officials complained that Taiwan authorities have not let their currency rise in value against the dollar as much as other currencies have done. A higher price for the Taiwan dollar would make Taiwanese goods more expensive and less saleable in the United States.endqua