Senate Foreign Relations Committee Chairman Richard G. Lugar (R-Ind.) will recommend a tentative list of economic sanctions against South Africa today when the committee begins work on legislation to pressure the white minority government to negotiate an end to the apartheid system of strict racial segregation.

Mark C. Helmke, Lugar's press secretary, said yesterday that the proposed sanctions include several measures already in place under an executive order signed by President Reagan last year and seven new steps aimed at "hitting the white South African government and its infrastructure" without requiring a total U.S. withdrawal from the country.

He said the new steps would include a ban on imports to the United States of South African steel, uranium, cement and aluminum, which are all produced by government-controlled firms; lifting U.S. landing rights to South African Airways; freezing the U.S. bank accounts of the government-controlled companies, their employes, and employes of the South African government; and denying U.S. visas to these employes.

The other proposed new measures, Helmke said, include authorizing Reagan to sell U.S. gold reserves, a key commodity in the South African economy, and banning new investments in South Africa by U.S. companies that do not adhere to the so-called Sullivan principles on nondiscrimination in employment and housing practices.

The measure would also allow U.S. firms to sue for damages under U.S. and international law if the sanctions cause them to lose South African business to foreign competitors.

These proposed steps go beyond existing sanctions or new steps thought to be under consideration by the Reagan administration, which, under intense congressional pressure, has indicated a willingness to consider a modest increase in U.S. pressure on South Africa. National security affairs adviser John M. Poindexter met on Capitol Hill with Senate Majority Leader Robert J. Dole yesterday to discuss pending foreign policy issues, including South Africa. White House officials said Poindexter planned to discuss proposals to send a special U.S. envoy to South Africa to impress on the government the seriousness of the efforts under way here to agree on new sanctions.

Helmke, who described the proposed Lugar measures as a starting point for committee discussions that could lead to tougher sanctions, said, "We're not ruling out additional sanctions if they fit the theme. The theme is to hit the white government and its infrastructure. It is aimed at convincing the white government and its supporters to begin negotiations with the blacks."

Under Lugar's proposal, the sanctions would be lifted if South Africa took certain steps, including lifting its state of emergency, legalizing all political parties and releasing Nelson Mandela, the imprisoned head of the outlawed African National Congress.

The Foreign Relations Committee will meet in closed session today to discuss Lugar's proposals and others. Helmke said the committee is scheduled to draft sanctions legislation Thursday.

However, the future of any sanctions bill remains murky because of parliamentary maneuvering. Democrats are pushing a House-passed bill that would impose an almost total U.S. trade embargo on South Africa and require U.S. firms to withdraw from there.

The Democrats have threatened to attempt to attach this measure to legislation now on the Senate floor to lift the government's debt ceiling. If they do that, Dole said yesterday, he will immediately bring up another bill to supply $100 million in aid to the Nicaraguan rebels, which liberal Democrats have threatened to filibuster.

Thus, a Democratic filibuster over Nicaragua could block action on the sanctions legislation.

The president imposed limited sanctions against South Africa last year. These steps, which are due to expire in September, would be extended indefinitely in the Lugar proposal.