Administration officials, faced with escalating racial violence in South Africa and congressional pressure to act, indicated yesterday that President Reagan is unlikely to veto the imposition of U.S. economic sanctions, although he remains opposed to them in principle.

Both the House and the Senate overwhelmingly approved sanctions earlier this month as a largely symbolic way to oppose South Africa's apartheid policy of racial segregation. Senate Foreign Relations Committee Chairman Richard G. Lugar (R-Ind.) yesterday scheduled a House-Senate conference committee meeting for Wednesday to work out differences between the bills.

Senate Republican aides said it was possible the White House would impose some of the Senate version without waiting for Congress to act, in part to demonstrate a stand against apartheid and in part to forestall the conferees from agreeing to unacceptably tough measures.

White House officials would not rule out immediate action, but said they were waiting for a congressional verdict before deciding what to do.

The threat of a presidential veto has largely evaporated as a result of South Africa's new state of emergency, which has led to police clashes with the black majority population, nearly 500 deaths and 1,215 arrests, most of them involving blacks, officials said.

State Department spokesman Charles E. Redman said U.S. policy toward South Africa is undergoing "continuing reassessment" because of the "quite serious" situation there, but he reiterated administration opposition to "additional punitive sanctions" against the Pretoria regime.

"Dialogue between the government and the nation's black leaders is the only way out of the crisis that South Africa faces," Redman said.

Lugar delayed appointing Senate conferees on sanctions legislation for nearly two weeks while pressing the House to accept the milder Senate approach. If a committee compromise includes any of the tougher House provisions, he said, Sen. Jesse Helms (R-N.C.) will lead a filibuster and delay passage at least until September.

House aides said yesterday that the House conferees were ready to run that risk. "People are willing to wait until September if we can get something worth waiting for," one said. The 80-to-12 Senate vote for sanctions on July 11 indicated there would be strong support to shut off a filibuster, the aide said, and a vote could take place when Congress returns from its August recess.

Speculation on the shape of the final bill centered yesterday on provisions involving South Africa's krugerrand gold coin.

The Senate-passed sanctions include a ban on new U.S. bank loans and exports of nuclear technology and would further curb computer sales to South Africa. U.S. firms there would be required to "take an active role" in opposing apartheid, and any with more than 25 workers would have to observe a tougher version of the so-called Sullivan principles, which mandate pay raises, desegregation and promotions for blacks.

The measure would allow consideration of further sanctions in 18 months, including a ban on krugerrand imports and on new U.S. private investment in South Africa, if no progress is made toward ending apartheid.

The House version would ban krugerrand imports and new investment immediately.