President Reagan Thursday renewed his opposition to a plant-closing provision of the trade bill, saying Congress should not legislate a requirement that companies warn workers of planned shutdowns.

Shortly after his top trade negotiator repeated Reagan's plan to veto the just-passed trade legislation, the president was asked what quarrel he had with the worker-notification provision."As an old labor union president, I suggest that's a matter that belongs in the management-labor contracts between the unions and the people," the president said. Reagan was questioned as he greeted Canadian Prime Minister Brian Mulroney for a private lunch.

Reagan is a former president of the Screen Actors Guild.

U.S. Trade Representative Clayton Yeutter said earlier that Reagan would veto the massive trade bill, but congressional Democrats called on the president to "rethink his position" and sign the measure.

"This bill isn't dead yet," Senate Majority Leader Robert C. Byrd, D-W.Va., told reporters Thursday. "The ball is in the White House court. If there is a demise of this bill it will occur at the White House, not here."

House officials said it would be next week before the 1,000-page bill could be put into proper form and delivered to the White House. Reagan would then have 10 days to either sign it or veto it.

The bill would increase the power of the U.S. trade representative to act against other countries that use unfair trade practices, make it easier to curb imports, repeal the windfall profits tax on oil companies, and increase agricultural subsidies.

Yeutter said Reagan will veto the bill because of the controversial plant-closing provision. He urged that the Senate eliminate that provision "very quickly."

"We need a trade bill this year," Yeutter said on NBC-TV's "Today" program.

"There are a lot of good things in that legislation, so if a couple of necessary corrections are made and the bill comes back, I'm really quite confident the president would sign it," Yeutter said in another interview on "CBS This Morning."

Byrd, however, said the Senate had only about 90 legislative days left this year and had a heavy schedule. Asked if it would accept proposed changes from the White House, Byrd said, "we're not spoon-fed from the White House."

"I hope the president will rethink his position and come down on the side of the American people," Byrd said.

House Speaker Jim Wright, D-Texas, pleaded for Reagan to sign the bill, which he said has overwhelming popularity across the country.

Wright said Reagan's promise to veto the bill was made to "captains of industry" who would understand if he changed his mind.

The governments of Japan and Korea Thursday urged Reagan to veto the measure. There was also a warning from the European Economic Community of retaliatory action if Reagan doesn't kill it.

Japan's chief government spokesman, Keizo Obuchi, said the bill which imposes sanctions against Toshiba Corp. may hinder world economic development. "The government of Japan strongly hopes that such a bill will not finally be enacted," said Obuchi.

South Korea Foreign Ministry spokesman Kim Hwang-kyung said the bill would hinder international trade and the government hopes the Reagan administration "will take appropriate actions in line with its much publicized stand on the bill."

Willy de Clercq, EEC commissioner for external trade, said the EEC "will react" to measures in the bill it considers protectionist and harmful to European interests if Reagan does not veto it.

The Senate approved the bill 63-36 Wednesday. That left Democrats at least three votes short of the two-thirds majority needed to enact their version over Reagan's objections.

The bill would get Reagan's signature, said Yeutter, if it were not for the provision, strongly backed by Democrats and labor, requiring companies to give workers 60 days notice of intended plant closings.