WASHINGTON -- President Bush signed the North American Free Trade Agreement yesterday, and his successor-in-waiting Bill Clinton immediately announced that he would not seek the treaty's renegotiation.

Mr. Clinton, in a statement issued in Little Rock, Ark., said the signing represented "an important step" toward the economic integration of North America. He repeated his campaign assertion that there would have to be new job and environmental protections, and safeguards against sudden trade "surges," but these could be settled without renegotiating the treaty with Mexico and Canada before he submitted implementing legislation.

"I will pursue those other things that I think need to be done in the public interest, then I will prepare implementing legislation and try to pass it in Congress," he said.

His new administration would also take domestic action on assisting workers, protecting the U.S. environment, helping farmers, encouraging public participation in consideration of the agreement and closing loopholes for foreign workers, he said.

"I believe these steps do not require renegotiation of NAFTA," said Mr. Clinton, promising to work closely with the two neighboring governments and with congress to "move this process forward."

By putting his name to the pact that will open the borders of the United States, Mexico and Canada to a market of 360 million consumers with a joint annual output worth $8 trillion, Mr. Bush took some of the heat from the agreement's critics off the president-elect.

"I think probably Bill Clinton is relieved that Bush signed it today," said Thea Lee, trade expert at the labor-backed Economic Policy Institute. "Clinton is on record as saying he does not want to renegotiate the basic agreement. Now Bush has tied that up for him but has left him quite a bit of room for maneuver in drafting implementation legislation."

The AFL-CIO, which is bitterly opposed to the treaty as a threat to U.S. jobs, announced it would continue its battle to kill the treaty in its entirety in Congress.

The treaty is also opposed by a broad alliance of environmental and consumer groups, which this month launched a national advertising campaign against it.

Critics of the treaty say U.S. jobs will be exported to Mexico where pay is lower, and worker health and safety standards are less strict. Environmentalists also fear that U.S. companies will be lured to Mexico by its lower air, water and land pollution safeguards, and this would worsen cross-border pollution.

Mr. Bush's action yesterday fulfilled the requirements of the "fast-track" legislative process, under which Congress can now only vote the agreement up or down. It cannot change the signed document.

Mr. Bush had to allow Congress 90 days to consider the agreement before signing. Yesterday was the first possible day for his signature. The clock will start ticking again when Mr. Clinton submits implementing legislation to make the necessary changes in U.S. law and tariffs required by the treaty. There is no deadline for Mr. Clinton to take this action, but once he does Congress will have up to 90 legislative days to vote up or down on the implementing legislation or change it.

The vote on the implementing legislation will ratify the treaty, which is due to go into effect Jan. 1, 1994.

"The focus of the debate now . . . would be what needs to get done before or in connection with implementation of what has already been signed, not what of that needs to be taken apart," said D. Holly Hammonds, trade expert with the pro-Clinton Progressive Policy Institute.

Part of that debate could focus on Baltimore's Domino Sugar plant, which employs 800 people. Under NAFTA, if Mexico turns out to have been a net exporter of sugar to the United States in two of the first seven years of the agreement, the U.S. market will be opened permanently to Mexican sugar. Currently, Mexico is a net importer of sugar because it sweetens all its sodas with sugar. But if it followed the U.S. lead and switched to U.S. corn syrup, it would have vast amounts of sugar to export, which could flood into the United States, threatening Domino's share of the market.

Rep. Benjamin L. Cardin, who represents the 3rd District around the Domino plant, has raised the danger with the U.S. trade representative, who has said the fear of a deluge of Mexican sugar is unfounded.

"We are going to fight for the Domino sugar issue," Mr. Cardin said yesterday, indicating that he would seek to ensure "an even playing field" between U.S. and Mexican sugar producers through the implementing legislation.

President Bush, signing the treaty, said yesterday: "I believe the time will come when trade will be free from Alaska to Argentina, when every citizen of the Americas will have the opportunity to share in new growth and prosperity."

At similar ceremonies yesterday in Ottawa and Mexico City, Canadian Prime Minister Brian Mulroney and Mexican President Carlos Salinas de Gortari put their names to the treaty.