President Trump calls them “signing bonuses” and they have emerged as the most effective way for wealthy trade partners to complete deals with the world’s largest economy.

It started when Japan declared it would establish a $550 billion fund for investments in the United States. Following suit, the European Union indicated its companies were poised to invest at least $600 billion. On Wednesday, South Korea pledged to create a $350 billion investment fund.

But now, a little over a week after the Japan deal was announced, significant discrepancies have emerged between how the United States and its trade partners are interpreting the spending commitments, underscoring the tenuousness of these flashy pledges.

For Japan, its commitment to establish a fund for U.S. investment proved a pivotal factor in securing a more favorable, lower-than-threatened tariff rate of 15 percent. Nevertheless, from the deal’s announcement last week, Japanese and American officials appeared to hold diverging views on the specifics of the investment plan.

In revealing the U.S.-Japan agreement in a social media post, Mr. Trump said that in exchange for the reduced tariff, Japan would funnel $550 billion, at his direction, into the United States, with America expected to receive 90 percent of the profits.

Ryosei Akazawa, Japan’s chief trade negotiator, conveyed a different message back to Tokyo: Japan would offer a blend of investment, loans and loan guarantees, totaling up to $550 billion, with profits to be allocated based on each side’s committed risk and financial contribution.