Colombia, the only large South American nation to avoid an international debt crisis, has reached a pioneering $1 billion loan agreement with about 200 commercial banks to be monitored by the International Monetary Fund, Colombian and monetary officials said yesterday.

The IMF board agreed after a lengthy meeting Friday to take on a new role -- that of monitoring the implementation of an adjustment program drafted by the Colombian government and using money provided entirely by commercial banks.

Other Latin American countries have negotiated debt-refinancing agreements that are to be monitored by the IMF, but this is the first loan agreement that does not involve rescheduling, officials said.

The money, earmarked for 1985 and 1986, is to be used for development projects, including large coal and oil enterprises, Rodrigo Lloreda, Colombia's ambassador in Washington, said.

Colombia's external debt of about $10.5 billion is much lower than that of comparable South American countries because of what one official called its "very prudent economic policy." It is the only Latin American country that has been able to make prompt payments on both its interest and principal in recent years.

Colombia already has begun its economic adjustment program by increasing taxes, raising gasoline and utility prices and implementing a salary increase for public employes that is lower than the 25 percent annual inflation rate. The government also accelerated the process of regular devaluations of the peso.

Lloreda said Colombia's policy is to limit loans from commercial banks to "25 percent of our external financial needs." He said the rest is supplied by international banks, bilateral aid and supplier credits. The loans from international banks and governments have easier payment terms, making Colombia's total interest payments lower than those of its neighbors.