Ryosei Akazawa, Japan's chief tariff negotiator, is off to Washington again on Thursday as the United States promises clarity by the end of the week on Japan's $550 billion investment pledge.

It will be his 10th trip to the U.S. since tariff negotiations started in April, and the second time since the two countries reached a last-minute trade deal on July 22.

U.S. Commerce Secretary Howard Lutnick said on Tuesday in the United States that an agreement on the $550 billion pledge — which was made by Japan in the course of negotiations as a concession to get tariffs lowered — will be released later this week.

Officials in the U.S have described the pledge as involving “all new capital” from Japan being invested in the U.S., with America in control and taking 90% of the profits. The United States has also said that tariff rates will be taken higher if the agreement is not implemented.

“You're going to see a national and economic security fund built with the Japanese money, the Korean money and other countries' money," Lutnick said in a CNBC interview on Tuesday.

"They're going to give us money to build our infrastructure out in America,” he continued. “Those are the deals that Donald Trump made using his tariffs — not using the money from the tariffs, but using the commitment of these countries that fundamentally understand a strong and powerful America is necessary for the world to be successful.”

Japanese officials have said that Japan will provide loans, loan guarantees and equity investment up to $550 billion — which is more than Japan’s tax revenue last year — via government-backed financial institutions.

Akazawa has also said that direct equity investment will be just 1%-2% of that total.

Japanese officials have expressed concern that the tariff on automobiles has not yet been lowered — from the pre-agreement total of 27.5% to the agreed upon 15% — while the reciprocal rate has already been upped to 15% from the baseline rate of 10%.

They have also been preoccupied with the issue of whether the tariff deal with the United States should be in writing or not.

“My understanding is that between Japan and the U.S., it is the U.S. side that feels more strongly about creating such a document, or sees greater merit in doing so,” Akazawa said at a news conference on Tuesday.