By Missy Ryan WASHINGTON, April 25 (Reuters) - Japan needs to act swiftly to open its markets to more U.S. beef imports, U.S. lawmakers said on Wednesday, a day before President George W. Bush hosts Japanese Prime Minister Shinzo Abe. The April 26-27 visit, Abe's first official trip to Washington, "is going to smoke out the Japanese whether or not they're keeping our meat out for political reasons or for food safety reasons," said Sen. Chuck Grassley, the top Republican on the Senate Finance Committee. "They ought to move forward in taking our meat without any restrictions," the Iowa senator told Reuters. Grassley's comments reflect growing impatience among U.S. politicians and industry groups about Japan's continued refusal to accept U.S. meat from animals older than 20 months old because of mad cow worries. The U.S. beef industry is eager for the return of a robust market with Japan as well as with South Korea, another country which has been skittish about renewing trade. U.S. companies had a $1.4 billion-a-year export market before 2003, when mad cow disease was discovered in the United States. For 2006, that figured stood at $66 million. U.S. companies also have felt rankled by Japan's mandatory inspections of each box of beef shipped, which slows trade and adds costs. FRONT BURNER ISSUE? Grassley told President Bush in a letter this week that "it is patently clear that U.S. beef is safe." Grassley's colleagues from Montana, Democrat Sens. Max Baucus and John Tester, meanwhile, wrote the White House chef suggesting beef from their state be served for Abe's visit. But many in the agriculture community don't expect change until after a ruling next month from the World Organization for Animal Health (OIE), which is expected to formally classify the United States as a "controlled risk" country. Earlier this week, the Agriculture Department announced it would allow Japan to inspect U.S. beef processing plants, which puts the United States one step closer to its goal. Agriculture Secretary Mike Johanns said the inspections would pave the way for dropping the mandatory inspection requirement. The U.S. Meat Export Federation, an industry group, cheered the move and predicted doubled meat exports. The National Cattlemen's Beef Association said it would be watching for any news following Bush and Abe's meeting. "Japan could be a lucrative market for U.S. cattlemen once again, but the road toward achieving that goal has been long and time-consuming," the group said.