WASHINGTON, May 14 (Reuters) - The Bush administration is disappointed by South Korea's decision to delay acceptance of U.S. beef exports, a trade official said on Wednesday, pushing Seoul to comply with a hard-won deal for resuming beef trade.

"We are disappointed as we understand Korea is planning to announce tomorrow a temporary delay in implementing the protocol agreed to April 18th," Gretchen Hamel, a spokeswoman for Trade Representative Susan Schwab, said in an e-mail.

"We understand that Korea will need more time to review (public) comments ... We expect the Korean government to live up to the agreement," she said.

Just last month, the administration heralded a long-desired accord with South Korea that would relax its import rules for beef, seemingly smoothing the way for resumed beef exports to a lucrative market and removing a stubborn obstacle to Congress' consideration of a major bilateral trade deal.

South Korea, which was the third largest importer of U.S. beef until the discovery of mad cow disease here in 2003, was scheduled to begin quarantine inspections from Thursday, which would have led to the first full imports of U.S. beef in more than four years.

But facing sharp public safety concerns, the South Korean farm ministry said on Wednesday said it would need perhaps another week to 10 days before that could occur.

Last week, the South Korean prime minister and other top officials apologized on national television over the issue, promising that a beef ban would return if there was another mad cow outbreak in the United States.

Beef trade was supposed to have resumed long ago for certain U.S. products, including boneless beef from animals 30 months old or younger, but even that trade had been stymied due to U.S. shipment snafus.

Once trade resumes, U.S. beef exports to South Korea are expected to reach as high as $1 billion a year.

"The level of our disappointment is hard to describe," said Gregg Doud, an economist with the National Cattlemen's Beef Association. He said no U.S. beef has been shipped to South Korea since the agreement last month.

The United States has insisted that all trading partners should drop import restrictions, especially after an international animal health agency gave it a new safety rating last year.

U.S. Sen. Max Baucus, who chairs the Senate Finance Committee, which has jurisdiction over trade deals, lashed out at news of the delay.

"I respect Korea's political process but there's no legitimate reason to delay importation of U.S. beef any longer ... Delaying implementation of this protocol is unhelpful to our countries' economic relationship," he said.