Brazil and its creditor banks reached an agreement last night under which Brazil will resume payments on its $67 billion in commercial debt, which it suspended last February, sources said.

The agreement, under which Brazil will supply $500 million of the $1.5 billion payment for the fourth quarter of 1987, with banks lending the rest, does not settle the disputed issue of how Brazil will pay the roughly $3 billion in back interest it has built up this year. Nor does it deal with Brazil's longer-term request for $10.4 billion in new loans over the next three years.

But sources said Brazil has agreed to allow the International Monetary Fund to oversee its economic policies, a significant political concession for the Brazilian government and one sought hard by the banks.

U.S. government sources said, however, that the announcement of Brazil's intentions to go to the IMF is likely to be made in such a way that it does not appear the nation is backing down. There has been much internal controversy in Brazil over whether it should go to the international agency for supervision of its domestic economic policies.

Negotiators hope that the agreement, reached over several weeks of meetings between a committee of lender banks and Brazilian financial officials, will persuade federal regulators not to downgrade the rating of Brazilian loans. The regulators, who met in secret last week, have the power to order banks to place a portion of their Brazilian debt in a special "value impaired" reserve, which would reduce the banks' earnings.

Brazil owes about $111 billion to its public and private creditors, making it the largest Latin American debtor. The nation has been building up cash reserves while it has run a trade surplus in recent months, but officials until recently had been discussing making a token payment to some kind of international escrow account rather than to the banks themselves.

Sources said the $1 billion the banks would lend to Brazil to partially fund the interest payment would become part of the longer-term new lending package that is still the subject of negotiations.