A split between supermarket and restaurant chain operators over Japan's import ban on U.S. beef widened Wednesday after a group of midsize supermarket operators asked the government not to compromise in its efforts to make the United States test all cattle for mad cow disease.

Blanket testing of cattle for mad cow disease is "a question of safety rather than profit and loss or economy," said Nobutsugu Shimizu, chief executive officer of the Japan Supermarket Association, after his meeting with Yoshiyuku Kamei, minister of agriculture, forestry and fisheries.

During the meeting, Shimizu gave Kamei a letter from the association that supports the government's demand that the U.S. test all cattle for the disease, formally known as bovine spongiform encephalopathy, before Tokyo will remove the import ban it imposed in December after the discovery of the brain-wasting disease in the U.S.

Kiwamu Yokokawa, chairman of the Japan Food Service Association, on Tuesday criticized the farm ministry for rejecting a U.S. proposal to ask the Paris-based Organization for Animal Health to mediate the stalled beef talks between Japan and the U.S.

Yokokawa called Japan's rejection of the proposal "extremely regrettable."

He said the ministry should give top priority to the removal of organs most susceptible to BSE, such as the brain and spinal cord, to secure the safety of U.S. beef shipments to Japan.

The row over the import ban between the two associations got under way when the supermarket association sent a letter to lawmakers Monday expressing its firm support for the testing of all cattle for BSE.