The agreement came just hours before leaders of the two countries were to meet in Washington. The beef issue had been a key dispute between the allies, and had threatened prospects of approval of a wider free-trade agreement.
The South Korean Agriculture Ministry said Friday that Seoul would allow American beef imports from cattle younger than 30 months, including cuts with bones. Younger cows are believed to be less at risk for mad cow disease.
South Korea will allow beef from older cattle after the U.S. strengthens controls on feed to reduce chances of infection.
The reported breakthrough came as new South Korean President Lee Myung-bak prepared to start his first summit with U.S. President Bush on Friday in the United States.
Yonhap said Seoul has agreed to relax quarantine regulations to allow imports of rib bones and beef of all ages. It was not clear if Seoul would allow imports of other previously banned parts, such as spinal columns, skulls and intestinal parts believed at risk of carrying the brain-wasting disease that may pose a danger to humans.
The American Chamber of Commerce in Korea said in a statement that South Korea had agreed to allow beef of all ages and all cuts.
"The previous Korean government had promised to open the beef market over and over again for over two years, but did not keep their promise," chamber Chairman William Oberlin, who was accompanying Lee in the U.S., said in the statement. "However, President Lee, who has only been in power for less than two months, made this possible."
The U.S. has demanded Seoul fully open its beef market, saying it is needed for congressional leaders in Washington to back a free-trade accord that the two countries signed last year. Washington has also argued that American beef has been certified as safe by the Paris-based World Organization for Animal Health.
South Korea suspended U.S. beef imports in 2003 after mad cow disease was discovered in the U.S, cutting off what was then the third-largest market for American beef.
Restricted imports resumed last April, but have been on hold since October when a shipment contained animal parts that have been banned over mad cow concerns.
Closer Ties To Seoul:
Oberlin's praise was indicative of the mood of hope in both capitals about increasing cooperation between the countries.
After years of uneasy relations with South Korean leaders whom the White House considered soft on North Korea, President Bush will warmly welcome on Friday a South Korean counterpart who talks tough about the North.
Mr. Bush and Lee will be eager to signal a new, cooperative tone as they push a reluctant Congress to ratify an ambitious free trade deal, work to settle a spat over South Korea's ban of American beef and discuss ways to persuade North Korea to fulfill commitments in six-nation nuclear negotiations.
The Washington Post reported Friday that Lee will propose creating a permanent high-level diplomatic channel between the North and South, including establishing the first liaison offices in the nations' capitals after nearly six decades of division.
Lee embraced the recent U.S. proposal to have North Korea "acknowledge" U.S. concerns and evidence about its apparent efforts to enrich uranium and its suspected nuclear trading with Syria, rather than provide its own dossier on such activities, the Post said.
Lee said the solution would offer North Korea "an indirect way to being involved in these two activities," therefore allowing the stalled negotiations to move forward.
With only nine months left in Mr. Bush's presidency, and with the nuclear talks at an impasse, it may be too late for the leaders to settle a top foreign policy goal for the Bush administration: a deal to rid North Korea of its atomic bombs.
He has ended a decade of liberal rule in which South Korea sought to embrace the North and refrained from criticism. The relief in Washington has been evident in the Bush administration's praise of Lee's insistence that the North follow through on nuclear pledges before receiving aid from its southern neighbor and rival.
Now, however, Lee's position on North Korea may turn out to be even tougher than Mr. Bush's as the United States presses hard for an agreement.
The highlight of Lee's Washington visit will come when he is feted at the Camp David presidential retreat in mountains north of the capital. Jack Pritchard, the State Department's special envoy for North Korea negotiations until 2003, said at a recent conference that the Camp David invitation is an "extraordinary symbolic gesture and a guarantee of success of the summit, even if they just showed up and shook hands."
Several other signs also point to the leaders hitting it off. Bruce Klingner, a Northeast Asia analyst at the Heritage Foundation, said in an interview that both men are former businessmen with conservative free-market ideas; both are Christian; both say they want to hold the North accountable to its nuclear pledges; and both view the U.S.-South Korean relationship as crucial to Asian security.
By contrast, Mr. Bush's meetings with Lee's predecessor, Roh Moo-hyun, who was elected on an anti-America platform, were often notable for their awkwardness, fueling the perception that the leaders did not like each other. Roh favored a so-called "sunshine" policy that provided aid without demanding concessions from North Korea.