The US is expected to face difficulty in convincing Japan to fully reopen its beef market to imports but forward progress is still possible, according to US Agriculture Secretary Tom Vilsack.

"I have no illusions how easy this is going to be. It's obviously going to be difficult," Vilsack told a press briefing ahead of his trip to Japan next week.

Nonethesless, Vilsack said he expects forward progress regarding Tokyo's controls on US beef imports, which stem from fears about mad cow disease, when he meets Japanese officials such as Agriculture, Forestry and Fisheries Minister Hirotaka Akamatsu.

"We would never make a demand. This is a relationship that has been bound in friendship for an extended period of time, and it is really about friends basically talking to each other about each other's needs," he said.

Japan and the US are at odds over Washington's insistence that Tokyo abolish its ban on imports of US beef from cattle aged over 20 months.

Vilsack is due to travel to Japan for five days starting next Monday (Apr 5) as part of a new initiative by President Barack Obama's administration to double US exports over five years.