The Senate sent to the President yesterday, 66 to 26, a bill restoring the U.S. embargo against imports of chrome from Rhodesia.

The measure, passed by the House Monday, 250 to 146, has the strong backing of President Carter. It authorizes the President to reimpose the ban on imports of chrome from Rhodesia and thus put the United States back in compliance with U.N. sanctions against the white minority regime of Ian Smith.

First voted in 1966 by the United Nations, the embargo was beefed up in 1963, and President Johnson ordered an import cutoff in 1968. But Congress in 1971, heeding arguments from Sen. Harry F. Byrd Jr. (Ind.-Va.) that the United States vitally needed chrome from Rhodesia for industry and defense needs, voted to rescind the U.S. ban. Since 1971, the United States has been importing chrome from Rhodesia.

Sen. Dick Clark (D.-Iowa), floor manager of the bill, said restoration of the embargo would demonstrate that the United States backs majority rule in black Africa and will no longer give aid and comfort to the Smith regime's efforts to thwart it.

"It's a question of putting our best foot forward in Africa in a decade," Clark said. "When you go to Africa all they talk about is how we violate United Nations sanctions." Clark said the bill's supporters had made every effort to rush it through Congress before President Carter's scheduled U.N. speech Thursday.

Clark and other supporters of the bill said the United States isn't really in need of Rhodesian chrome imports because it can get plenty of chrome ore and ferrochromium alloys (a mixture of chrome and other metals) from other countries such as Turkey, South Africa, the Soviet Union, Brazil and the Philippines.

State Department witnesses told the Foreign Relations Committee that the United States has a strategic stockpile of nearly 4 million tons, well over a four-year supply for all purposes and enough to last many years more if confined to defense needs.

Byrd, James B. Allen (D.-Ala), Jesse A. Helms (R.-N.C.), and others argued that it was unwise to cut off a supplier of a vital metal, particularly as, according to Byrd, many other countries are ignoring various aspects of the trade embargo against Rhodesia, such as West Germany, Japan and Italy.

Allen said nobody had demonstrated that the U.S. participation in the embargo would really have much impact on Rhodesia's economy.

Clark said it wasn't so much an economic matter as putting the United States in compliance with a U.N. embargo resolution for which it had voted, of helping open a channel to black Africa for the United States and of moving to carry out the Carter policy of strengthening relations with black Africa.

The bill not only would restore the ban on direct imports of chrome from Rhodesia, but also would bar imports of steel-mill products from third countries which contain Rhodesian chrome. This is designed to protect the U.S. steel industry.

According to figures supplied yesterday by the Bureau of Mines, the United States imported from Rhodesia about 220,000 tons of chrome ore and ferrochrome alloys worth $45 million in 1975. The 1976 figures were 81, 000 tons and $25 million. The 1976 figures constituted 4.7 per cent of all U.S. chrome ore imports and 22 per cent of its ferrochromium imports in 1976, Clark said.

For Rhodesia, according to Clark, ore exports to the United States constituted only a tiny portion of its total ore exports (4 per cent), but ferrochromium exports to the United States constituted 31 per cent of Rhodesia's total ferrochromium exports.

The State Department said Rhodesia hasn't been publishing economic statistics in recent years, but one estimate put Rhodesian export goals for all products, not just chrome, at $500 million a year. Loss of the U.S. market would thus be a meaningful but not overwhelming loss, since only $25 million worth of chrome and ferrochrome were sent to the United States in 1976. The political impact of withdrawal of U.S. market would be far more important, department sources said.

The Senate added by voice vote anamendment, identical to one attached in the House the day before, permitting the President to reopen with Rhodesia if he thought it would "encourage meaningful negotiations" toward majority rule in Rhodesia. It was proposed by Byrd.

National staff researcher Jane Frevndel also contributed to this article.