Efforts to bar the Export-Import Bank from supporting U.S. exports to South Africa have been set back by the Senate Banking Committee's refusal to include that prohibition in legislation governing the bank's activities.

At a meeting Wednesday, the committee set aside an amendment proposed by Sen. Donald W. Riegle (D-Mich.). It would have halted the bank's programs in South Africa until that country makes progress toward ending racial segregation.

The Riegle amendment parelleled one adopted by the House Banking Committee Monday when it approved its version of a bill raising the bank's lending authority. The bank is a government agency whose purpose is to boost U.S. foreign trade by providing financing for overseas sales.

As a substitute for the Riegle amendment, the Senate Committee adopted a proposal by Sens. Adlai E. Stevenson (D-Ill.) and John Heinz (R-Pa.).

They said it would avoid singling out specific countries as targets of trade restrictions for political reasons. Instead, they added, their amendment is intended to provide a uniform standard for judging whether trade sanctions should be applied against any country.

Specifically, the president would be required to submit to Congress at three-year intervals a list of all countries that he considers eligible for Export-Import Bank financing. In compiling the list, he would take into account several factors involving each country's foreign and domestic policies, including human rights records.

Congress then could not act against individual nations on the list. It would have to accept or reject the entire list.

If it approves the list, the bank would be able to support exports to all countries on it. If the list is rejected, the bank could deal only with those nations previously receiving financing. All others would be barred until they were included on a new list approved by Congress.

Opponents of this approach charged that, if it prevails in the legislation ultimately adopted by Congress, it would have no effect on barring Export-Import Bank activities in South Africa.

The Carter administration, which opposes restricting South African trade at this time, could be expected to include that country in its list of eligible countries. Similarly, the opponents noted, Congress is not likely to turn down the entire list solely as a means of imposing sanctions against one country.

In a related human rights development yesterday, Rep. Thomas R. Harkin (D-Iowa) introduced legislation prompted by recent disclosures about U.S. banks lending large sums to Chile at a time when the administration has cut back Chilean aid because of that country's poor human rights record.

Harkin's bill would require all private banks to regularly inform the secretary of the treasury of their loans and investments in countries found to have engaged in consistent rights violations. This information, in turn, would have to be turned over to Congress.

In a Senate speech about Chile yesterday, Sen. Edward M. Kennedy (D-Mass.) characterrized the private bank loans as "shocking" and said they should be stopped. Otherwise, he added, he also would sponsor legislation to require disclosure of loans to countries that are rights violators.

Although he agreed that the Chilean military dictatorship has taken some steps toward improving the rights situation there, Kennedy said the Carter administration has been too quick to reward this movement with a loosening of the clamps on aid.