The U.S. ambassador welcomed the panel's recommendations, but the findings angered some Japanese consumer groups who said they were still worried about the safety of U.S. beef.
The panel's decision, if accepted by the government, will clear the way for Japan to begin importing U.S. grade A40 beef, which comes primarily from cattle aged 12 to 17 months.
Panel chairman Akihiro Okitani, a professor at the Nippon Veterinary and Animal Science University, told reporters there was a high probability that meat of this grade was free of mad cow disease.
Japan imposed a ban on U.S. beef imports in December 2003 after the United States discovered its first case of the fatal brain-wasting illness, known formally as bovine spongiform encephalopathy or BSE, in a Washington state Holstein.
Okitani praised information that U.S. researchers provided the panel to help it make its decision.
"The U.S. researchers came up with highly reliable data," Okitani said. He added it was up to the Japanese government to decide whether to lift the ban on beef imports.
U.S. Ambassador Howard Baker said he was pleased the panel agreed that using the "A Maturity" grading system was an effective method of ensuring meat from animals older than 20 months of age would not be exported from the United States to Japan.
"Now that we have finalized a major portion of the technical side of this issue, I call upon the Japanese government to work with us to expedite the remaining implementation process, so that we may all once again enjoy U.S. beef in Japan," Baker said.
Hirofumi Kugita, the director of the Agriculture Ministry's international animal and health affairs office, said it was unclear how soon Japan would lift its import ban. Japan's Food Safety Committee would consider the panel's recommendations, he added.
Consumer groups swiftly criticized the panel's decision.
"This conclusion was made politically and hastily in response to the American demand that we resume beef imports from the United States," said Yasuaki Yamaura, a senior official of Consumers Union of Japan.
Masae Wada, a spokeswoman for the national group Housewives' Association, said she was concerned there were too few beef grade inspectors in the United States to sufficiently guarantee meat safety.
"When you think how many cattle each one of them handles each day, it is hard for consumers to trust the results," Wada said. "The number of grade inspectors is too small."
Before the ban, Japan was the most lucrative overseas market for U.S. beef producers, buying $1.7 billion worth of beef in 2003.
The two sides tentatively agreed late last year to resume imports of beef products from cows younger than 21 months. Talks later stalled over differences about how to authenticate the age of cattle.
Japan said it would only accept beef from animals with a birth record. But U.S. beef producers do not keep such records for every animal, relying instead on birth records for herds and a grading system that uses tenderness of the meat to judge age.
Experts had narrowed those differences after U.S. officials proposed a method by which a cow's age can be determined by looking at the maturity of its skeleton.
The method, though not traditionally used to determine the age of cattle, has long been used by U.S. authorities as a de facto age marker when meat is being graded and tested for the market.
BSE is a brain-wasting illness that can be fatal to humans who eat contaminated beef.