WASHINGTON, April 23 (Reuters) - In a step aimed at expanding beef trade with Japan, the United States will allow Japanese inspections of U.S. beef plants, the Agriculture Department said late on Monday.

Audits of processing plant will begin as soon as possible, Agriculture Secretary Mike Johanns said in a statement.

"Once the verification process is complete, Japan will discontinue its requirement of inspecting 100 percent of the boxes of beef shipped from U.S. plants," he said.

The announcement comes days ahead of Japanese Prime Minister Shinzo Abe's first official visit to Washington.

Abe is due to meet with President George W. Bush later this week on a host of issues, including North Korea and Iraq. But the U.S. agriculture community wants to make sure the discussions also touch on beef trade.

Meat exporters have been working to rebuild their trade with Japan, which closed its market to U.S. beef at the end of 2003 when mad cow disease was discovered here.

Japan now accepts imports of U.S. beef from animals aged 20 months or younger, but U.S. exporters want to see meat allowed from cattle up to 30 months old. They also complain about the high costs of inspections for every box of imported meat.

"The United States expects Japan, as well as all of our trading partners, to implement import requirements for U.S. beef and beef products as soon as possible ... based on science and consistent with international guidelines," Johanns said.

U.S. official hope that a ruling expected next month from the World Animal Health Organization (OIE), which would give the United States a "controlled risk" rating, will ease a loosening of those rules.

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