Donald Trump announced Tuesday a "massive" trade deal with Japan, as a deadline looms for other major US trade partners to strike agreements before the end of the month.

In an attempt to slash his country's colossal trade deficit, the US president has vowed to hit dozens of countries with punitive "reciprocal" tariffs if they do not hammer out a pact with Washington by August 1.

The Japan agreement, along with another pact with the Philippines also announced on Tuesday, means Trump has now secured five agreements since his administration promised in April "90 deals in 90 days."

The others were with Britain, Vietnam and Indonesia, which the White House said Tuesday would ease critical mineral export restrictions.

"We just completed a massive Deal with Japan, perhaps the largest Deal ever made," Trump wrote on his Truth Social platform.

He said that under the deal, "Japan will invest, at my direction, $550 Billion Dollars into the United States, which will receive 90% of the Profits".

He did not provide further details on the unusual investment plan, but said it "will create Hundreds of Thousands of Jobs".

Japanese exports to the United States were already subject to a 10 percent tariff, which would have risen to 25 percent on August 1 without a deal.

Duties of 25 percent on Japanese autos -- an industry accounting for eight percent of Japanese jobs, were also already in place, plus 50 percent on steel and aluminium.

Japanese Prime Minister Shigeru Ishiba said that the autos levy had now been cut to 15 percent, sending Japanese car stocks soaring, with Toyota and Mitsubishi up around 14 percent each. The Nikkei rose 3.5 percent.

"We are the first (country) in the world to reduce tariffs on automobiles and auto parts, with no limits on volume," he told reporters.

"By protecting what needs to be protected, we continued the negotiations with an aim to reach an agreement that meets the national interest of both Japan and the United States," Ishiba added.