U.S. Trade Representative Robert Lighthizer on Thursday conveyed Washington's concern about Tokyo's recent imposition of emergency tariffs on frozen beef from the United States and other countries.

Lighthizer raised the issue of the so-called safeguard tariffs — under which Japan boosted the rate to 50 percent from 38.5 percent for the period from Aug. 1 to March 31 — in a meeting with Japanese Foreign Minister Taro Kono in Washington, the Office of the USTR said.

U.S. exports of beef and beef products to Japan totaled $1.5 billion last year, making it the United States' top market, according to the U.S. Agriculture Department.