U.S. President Donald Trump has suggested to The Wall Street Journal that he will take on Japan next in his fight to cut trade deficits with trading partners, according to a column carried on the paper’s online edition Thursday.

Citing a phone call he received from Trump, James Freeman, a columnist for the paper, wrote that the president “described his good relations with the Japanese leadership but then added: ‘Of course that will end as soon as I tell them how much they have to pay.’ “

Trade is likely to be a major topic when Trump meets Prime Minister Shinzo Abe around Sept. 25 on the sidelines of the U.N. General Assembly.

Even if Trump wraps up negotiations with Canada, Mexico and Europe, “the trade uncertainty won’t necessarily end,” Freeman wrote. “It seems that he is still bothered by the terms of U.S. trade with Japan.”

During the call, he wrote, the president sounded “still very focused on eliminating trade deficits with America’s trading partners,” in line with his “America First” agenda.

The Trump administration has pushed Japan to further open its automobile and agriculture markets as part of efforts to reduce the chronic U.S. trade deficit.

The column drew measured reactions from Japan. Deputy Prime Minister Taro Aso told reporters in Tokyo on Friday, “I don’t know President Trump’s relationship with The Wall Street Journal nor whether he actually said that.”

“We both have to do our part” to realize a fair trade relationship, added Aso, who doubles as finance minister.

Toshimitsu Motegi, the minister in charge of trade talks with U.S. Trade Representative Robert Lighthizer, said he is aiming for an arrangement that benefits both Japan and the United States.