The Carter administration yesterday formally denied that American commercial banks are becoming over committed in their loans to foreign countries - notably to lesser developed nations.

At the same time, to minimize the need for private lenders to assume "undue rusks," and as a way of disciplining borrowers, the United States is backing a major increase in the resources of the International Monetary Fund.

These points were made in testimony by C. Fred Bergsten, assistant secretary of treasury for international affairs before a House subcommittee.

Bergsten's optimistic assessment of the position of commercial banks amounted to an open disagreement with a statement made at the end of February by Federal Reserve chairman Arthur F. Burns.

Burns told a Congressional committee that he was becoming concerned that some banks might be over extended in their international lending and that he had issued such a warning to American bankers "in strident tones."

Burns' views, which are highly regarded in the international financial community, received wide circulation.

Without referring to Burns by name, Bergsten said that concerns of over exposure "are greatly exaggerated." The loss experience has been better on foreign than on domestic loans, he said, with foreign losses generally small.

Bergsten acknowledged that some changes are needed in the manner in which the world has been meeting the crucial payments problem created by the massive increase in the world price of oil since 1973.

The resultant surpluses of $40 to $65 billion annually accuring to the Organization of Petroleum Exporting Countries (OPEC), he said, must be met by reducing energy use and by a more rational way of financing the total non-oil world's deficit that will continue, despite energy reductions.

He reiterated the administration position that West Germany, Switzerland, Japan and the Netherlands must reduce their current account surpluses, which he estimated at $12 billion this year.

On the other side of the ledger, the Treasury official, said countries "with excessive current account deficits must also adjust."

For these nations, adjustment would mean a degree of austerity. For that reason. Bergsten told the committee, the U.S. believes that the IMF should take on a more important policing role and should acquire more resources to take pressure off the commercial banks.

These issues are top priority items for consideration at the economic summit meeting in London May 7 and 8. West German and Japanese leaders have expressed some resentment at what they consider excessive American pressure on them to lower their surpluses by accepting more imports or by airtailing exports. Japan's extraordinarily high volume of color television shipments to the U.S. is a current sore point.

Talking briefly to reporters after his testimony yesterday, Bergsten said that the IMF and its member nations were discussing a new lending "facility" in the neightborhood of $12 to $15 billion. Reports from Europe have estimated the new fund at 14 billion SDR (Special Drawing Rights) or about $16.6 billion.

Other sources yesterday said that a fund of that size would be contingent on getting 7 billion SDR advanced by the OPEC nations, including about 4 billion SDR from the richest of the oil countries, Saudi Arabia.

A variety of other ways to supplementing IMF resources, including a first-time borrowing from the private market in a manner similar to the World Bank, is being discussed. It is expected that a multifaceted resources scheme will be well on the way to technical approval by the time the IMF Interim Committee meets here April 28 and 29.

Bergsten stressed yesterday that enlarged international institutional lending would not diminish the role of the banks and others in the private markets, which have supplied about 75 per cent of the borrowing by deficit countries in the past three years.

He pointed out that the pace of "reschedulings," or postponement of payments, had actually declined in recent years despite the 500 per cent boost in world oil prices.

The lending activities of banks, he said, "have been remarkably successful in playing a vital role in helping to finance an uprecedented level of international trade.

"We can find no adverse effects on our own economy, the soundness of our banking system, the availability of credit for domestic purposes, or the entire would economy."