WASHINGTON, (Reuters) - Japan has agreed to ease restrictions on United States beef imports imposed nearly a decade ago in response to several cases of mad cow disease found in the American cattle herd, U.S. officials said on Monday.

"This represents a significant and historic step in expanding U.S. beef trade with Japan and growing American exports and jobs here at home," U.S. Trade Representative Ron Kirk said in a statement.

Effective Feb. 1, Japan will now permit the import of beef from cattle less than 30 months of age, compared to the previous limit of 20 months, among other steps.

It is estimated that these important changes will result in hundreds of millions of dollars in exports of U.S. beef to Japan in the coming years, USTR said.