TOKYO (Reuters) -U.S. Commerce Secretary Howard Lutnick said in a CNBC interview on Tuesday that documents memorializing trade agreements with Japan and South Korea -- a sensitive topic in Tokyo -- are "weeks away" from being ready.

Japanese Prime Minister Ishiba, who is facing calls to step down after the ruling coalition's loss in the July upper house election, has come under attack for not insisting on getting the details of the U.S.-Japan trade deal in writing.

He has said Japan skipped this to avoid delaying a reduction in U.S. tariffs on Japanese goods.

Lutnick told CNBC the United States has reached a common understanding with both Japan and South Korea on these trade agreements.

Under the deal reached last month, the U.S. agreed to reduce tariffs on Japanese car imports to 15% from the previous 27.5%, but did not announce when the change would take effect.