South Korea and the United States agreed Friday on final changes to their pending free trade agreement, clearing the last hurdle to the fast approaching deadline to sign the deal as thousands of workers took to the streets in protest.

South Korea has "decided to accept a U.S. proposal to change the agreement" to reflect new U.S. guidelines calling for stricter labor and environmental standards for free trade deals, the Ministry of Foreign Affairs and Trade said.

South Korean Trade Minister Kim Hyun-chong and U.S. Trade Representative Susan Schwab will sign the agreement on June 30 in Washington, the ministry said.

The two sides need to sign the deal by then for it to be considered by Congress under President George W. Bush's expiring special trade authority.

That "fast track" power prevents legislators from making any changes to the deal before voting on it. The agreement needs to be approved by lawmakers in both countries to take effect.

The Bush administration was racing to meet the Saturday midnight deadline to conclude all aspects of pending free trade deals with Peru, Colombia and Panama as well.

South Korea and the United States concluded their agreement in April after 10 months of tough negotiations, but scrambled since last week to agree on amendments requested by Washington just days ahead of the signing deadline. The U.S. needed to amend the deal to incorporate stricter labor and environmental guidelines agreed by the new Democratic majority in Congress and the Bush administration for free trade deals.

The new U.S. guidelines are "in line with the direction of (South Korea's) labor and environment policies" and "do not break the balance of the initial agreement," Lee Hye-min, Seoul's deputy chief negotiator said.

The two governments say slashing tariffs and other trade barriers will boost commerce between the two close allies.

Opponents, however, say the deal will squeeze workers in both countries.

In central Seoul, thousands of striking workers were joined by students and farmers to protest the trade accord, which they say will harm livelihoods.

Chong Hye-won, director of the international department of the Korean Metal Workers' Union, said around 20,000 protesters were at the scene, mostly members of her union. A police estimate was not immediately available.

Some 110,000 members of the 150,000-strong KMWU walked off the job for a second day Friday in opposition to the free trade deal, Chong said.

The union is the largest in South Korea, and includes workers of large companies like Hyundai Motor Co. as members.

Amid a rainy-season drizzle, protesters — wearing red head bands — lit fire on metal wires covered with gasoline-soaked cloth formed into the letters "FTA."

"I think the Korea-U.S. FTA will greatly change the quality of life for the general public," said Chung Kap-deuk, head of the KMWU. "We oppose the FTA since it will bring more poverty for the poor, while letting the rich accumulate more wealth."

The trade accord is the largest for the U.S. since the North American Free Trade Agreement more than a decade ago, and the largest ever for South Korea.