A little-known group within the Carter administration has succeeded, in a series of unannounced steps, in toughening the execution of U.S. policy on human rights.

In recent weeks the so-called Christopher Group, going beyond what Congress has mandated, has blocked a U.S. loan to Chile and has caused the government to vote against or abstain from approving multinational loans to Chile, Argentina, South Korea and the Philippines.

The group, consisting of representatives from several departments and headed by Deputy Secretary of State Warren Christopher, was set up to consider granting or withholding aid to countries with human rights problems.

Its recommendations are advisory, but the departments charged with carrying them out have accepted them, at least in the cases of the four nations. "After all, we are one administration," said an Agriculture Department official.

While the actions have had little impact on the economies of the four countries, a few of the decisions have evoked strong misgivings on the part of some administration officials and business leaders.

For instance, Terence A. Todman, assistant secretary of state for Latin American affairs, favored a $10 million Commodity Credit Corp. (CCC) loan sought by Chile so it could import surplus American wheat.

Since September the loan has been blocked on human rights grounds by the Christopher Group.

Todman declined to discuss the loan specifically but said in a recent interview:

"Poor, hungary, miserable people ought not to be denied food, health care, clear, water, medicine - the things necessary to life - just to make a point with a government. All you're doing is adding to their misery."

Milton Haskel, editor of the National Farmers Union Washington newsletter, called the loan-blocking decision "regrettable bacause U.S. farmers have a considerable surplus of wheat, and anything that inhibits trade is something we don't want to see."

Keith Miceli, executive secretary of the American Chambers of Commerce in Latin America, said the administration's human rights policy is "laudatory, a courageous initiative," but added that "in the real world, you have to considert he fact that the United States does have national interests, and those factors should be weighed."

Miceli warned that "reactionary forces in countries that the U.S. acts against may take out their frustration on the American business community in their countries."

Some administration officials considered it significant that the Christopher Group assumed jurisdiction over the CCC loan issue because it is almost a commercial deal. The CCC, which is the Agriculture Department's bank, extends credit at commercial rates but over a longer period - three years in the Chilean case - than a regular bank does.

Mark L. Schneider, deputy assistant secretary of state for human rights, defended the Christopher Group policy on the CCC proposal.

The group assumed jurisdiction, he said, "because while it's similar to a commercial loan, it still represents a U.S. program." He said the group did not formally act; "it just didn't approve the loan."

He added that the prevailing feeling was that "the U.S. government shouldn't provide support to a government that is a gross and persistent violator of human rights."

The group's policy in the case was advisory, but an Agriculture Department official said, "We accepted their view."

Other recent U.S. actions on human rights include:

A negative vote cast last week by Ralph A. Dungan, the U.S. representative on the Inter-American Development Bank, on a Chilean request for a $24.5 million loan from the IDB for roads and bridges. The loan was approved.

Venezuela, breaking Latin American solidarity for the first time one such votes, joined the United States in saying no, and a delegation representing eight European nations abstained.

A negative vote, also cast last week by Dungan, to a request from Argentina for a $65 million IDb loan for a petrochemical plant. That loan also was approved.

It was the third time that Dungan has voted to reject Argentine loan requests. In November he opposed a $36 million loan for a gas pipeline and on Dec. 1 he opposed a $53.9 million loan for a cellulose plant in northern Argentina - loans the IDB approved.

In each case, the Christopher Group decided that Argentina had not made sufficient progress in human rights to merit a yes vote from the United States.

Abstentions by Lester Edmond, U.S. representative to the Asian Development Bank, on a $1.7 million technical assistance loan to South Korea for its Asian Bay power project and on a $35 million loan to the Philippine National Development Pank for industrial credits.

The abstentions are considered significant since Secretary of State Cyrus R. Vance told Congress in February that while the administration was recommending military aid cuts to Argentina, Ethiopla and Uruguay on human rights grounds, it would not cut aid to other countries, such as South Korea, that are strategically important to the United States.

The Philippine abstention last month may have an impact. Philippine President Ferdinand Marcos told Washington Post correspondent Jay Mathews last week that he supports President Carter's human rights policy and does not condone any instances of torture or illegal arrest that may have occurred under the martial law he imposed in 1972.

Marcos added there would have been no abstention had U.S. officials been fully informed about human rights in his country.

The U.S. votes to abstain or say no on international bank loans to the four countries go beyond congressional policy because Congress did not consider those nations in its recent debate on foreign aid.

At that time, the House sought to prohibit international banks from using U.S. funds for loans to Vietnam, Cambodia, Laos, Cuba, Uganda, Mozambique and Angola. The Senate refused to go along, accepting Carter's argument that such a loan in the law would jeopardize the operation of the banks.

Finally, to break the impasse, Carter promised Congress that if it would instruct U.S. representatives on the multinational banks to vote against loans to those seven countries.

Congress agreed, and in an escalation of the policy, the Christopher Group is advising that such instructions be given on loans to other nations. Its advice apparently is being taken seriously by other departments besides State. Just as Agriculture has not pushed for the CCC loan to Chile, so the Treasury has told U.S. representatives to vote according to Christopher Group policy in the multinational banks.

Since the loans were ordinary capital loans at near-commercial rates, they could not be vetoed by the United States. But so-called soft loans, which are granted at low interest rates over long terms, can be.

Chile, knowing how the United States felt, decided last week to withdraw its request for a $14 million soft loan from the IDB for health facilities.

"Clearly, our actions in the International banks are causing countries to examine their human rights violations and appreciate the lengths the U.S. is willing to go to protest them," said a U.S. official.