TOKYO (Reuters) -Japan's government said on Friday that profits from a $550 billion investment package agreed in this week's tariff deal with the U.S. would be split between Japan and the U.S. according to the degree of contributions by each side.

The comment from a Japanese government official suggests the investment scheme would involve substantial contributions not just from Japan but also from the U.S. government or companies, though the structure of the scheme remains largely unclear.

The White House said earlier this week the U.S. would retain 90% of the profits from the $550 billion U.S.-bound investment and loans that Japan would make in exchange for lower tariffs on auto and other exports to the U.S.

The official told a briefing that resulting returns will be split 10% for Japan and 90% for the U.S. "based on the respective levels of contribution and risk borne by each side."

Similarly, Japan's top trade negotiator, Ryosei Akazawa, said on Friday that he understands the U.S. side seeking a 90-10 split of returns as a sign of its commitment to shouldering a large share of the contribution and risk.

"Some people are saying Japan is simply handing over $550 billion, but such claims are completely off the mark," he said.

Akazawa also said the final decision on profit sharing will rest with private-sector companies joining forthcoming investment projects.

According to the Japanese government, the U.S. investment package includes loans and guarantees from state-owned Japan Bank for International Cooperation (JBIC) and Nippon Export and Investment Insurance (NEXI).

A law revision in 2023 has expanded the scope of JBIC, making foreign companies key to Japan's supply chains eligible for loans from the bank.

The investment package will allow Japan to build resilient supply chains in the United States that benefit both countries in sectors key to national security, such as semiconductors, pharmaceuticals, steel and shipbuilding.

The U.S. is largely dependent on Taiwan Semiconductor Manufacturing Co for advanced chip manufacturing currently, raising economic security concerns due to Taiwan's geographic proximity to China.