TOKYO (Reuters) -Japan's top trade negotiator cancelled a visit to the United States at the last minute on Thursday, further delaying talks designed to finalise a $550 billion investment package offered by Tokyo in exchange for relief on punishing tariffs.

Ryosei Akazawa was due to fly to Washington to craft a written confirmation of the terms of the package, such as the split of investment returns between the U.S. and Japan, a government source previously told Reuters.

U.S. Commerce Secretary Howard Lutnick has also said there would be an announcement this week on Japan's investment.

"It was found that there are points that need to be discussed at the administrative level during coordination with the American side. Therefore, the trip has been cancelled," Japan's government spokesperson Yoshimasa Hayashi told reporters on Thursday.

Washington and Tokyo agreed in July to set a reduced 15% tariff on imports from Japan in exchange for the package of U.S.-bound investment through government-backed loans and guarantees, but details of its contents remain unclear.

While Trump has touted the package as "our money to invest" and said the U.S. would retain 90% of the profits earned, Japanese officials have stressed that the investments will be determined based on whether they will also benefit Japan.

Japanese officials have repeatedly said they would rather have an amended presidential executive order first to remove overlapping tariffs on Japanese goods before releasing a joint document on the investment details.

The United States has agreed to amend the July 31 presidential order to ensure that a 15% levy agreed last month on Japanese imports was not stacked on goods, such as beef, that are subject to higher tariffs.

U.S. officials have also said Trump would issue another order to lower tariffs on Japanese cars to 15% from 27.5%, but did not specify when.

"We are strongly requesting that measures be taken to amend the presidential order concerning mutual tariffs as soon as possible, and to issue a presidential order to reduce tariffs on auto parts," Hayashi added.

Japan's exports posted the biggest monthly drop in four years in July, driven by a slump in shipments to the United States. Reflecting the tariff damage, Japan cut its growth outlook for the year from 1.2% to 0.7% earlier this month.

Akazawa could head to Washington as early next week after the outstanding issues were resolved, a government source familiar with the negotiations said.