President Carter plans to sign an order approving the sale of 38 tons of enriched uranium to India, forcing a test of strength with Congress over policy on the spread of nuclear weapons.

That was the gist of what the Senate Committee on Foreign Relations was told behind closed doors yesterday by Deputy Secretary of State Warren M. Christopher and Gerard C. Smith, former director of the Arms Control and Disarmament Agency and now U.S. ambassador to the International Atomic Energy Agency in Vienna.

"They told us the president will issue the executive order approving the shipment sometime in the next two weeks," a member of the Senate committee said at the end of yesterday's closed session. "They told us it was essential to the conduct of foreign policy."

The disclosures yesterday by Christopher and Smith were the first signs that Carter plans to go ahead with the uranium for India since the Nuclear Regulatory Commission voted almost a month ago to bar the shipment. The unanimous vote set off such a strong reaction in Congress in support of the NRC that the White House held up approval of the shipment.

"I guess some people thought the White House might back down from shipping the uranium to India," said a key Senate aide who was at yesterday's closed session, "but there was no sign of any backing down here today."

Senate sources said that Christopher told the committee it was in the best interests of foreign policy to ship the uranium to India becuase of continued unrest in South Asia. He cited the upheavals in Iran and the Soviet invasion of Afghanistan.

Carter administration sources have said repeatedly that the United States must move to strengthen relations with India, especially in light of the recent agreement India made with the Soviet Union for a $1.6 billion purchase of arms.

"The holdup of this uranium shipment is at least an irritant to our relations with India," an administration source said at a background briefing to the press not long ago. "We would hope that by shipping the uranium this irritant would be removed."

The NRC voted to ban the shipment because India refuses to sign the treaty prohibiting the spread of nuclear weapons, refuses to open up its nuclear facilities to international inspection, and has held open the possibility that it will explode nuclear devices in the future. India tested its first one six years ago underground.

To hear some of the State committee members express it, there has been no change in India's policy despite repeated attempts by the State Department to force one.

"The administration has made no progress whatsoever with India on this issue," a member said. "Even when they asked India for a clarification of Prime Minister Gandhi's remarks on the future testing of nuclear weapons, they received none."