The International Monetary Fund on Monday forecast the world economy will grow 3.9 percent this year, unchanged from its estimate in April, but warned that rising trade disputes between the United States and its trading partners could pose a "threat" to global growth.

In its latest World Economic Outlook, the IMF projected Japan's economy will grow 1.0 percent in 2018, down 0.2 percentage point from the previous outlook, dragged down by weak private consumption and investment in the January to March quarter.

The 2018 growth estimate for the United States was unchanged at 2.9 percent and that for China was kept at 6.6 percent, it said.

IMF chief economist Maurice Obstfeld expressed concern about the outlook of global economic growth, saying that amid escalating tensions over international trade, "the broad global expansion that began roughly two years ago has plateaued and become less balanced."

"The risk that current trade tensions escalate further -- with adverse effects on confidence, asset prices and investment -- is the greatest near-term threat to global growth," Obstfeld said.

U.S. President Donald Trump's administration plans to impose 10 percent tariffs on an additional $200 billion in Chinese imports as soon as September in response to Beijing's alleged intellectual property and technology theft, as well as the massive and chronic U.S. trade deficit with China.

Earlier this month, Washington invoked additional 25 percent tariffs on $34 billion in Chinese products. Beijing immediately retaliated with a similar action.

Obstfeld said an IMF modeling suggests that if U.S. trade policy threats to China, the European Union, Japan, Canada, Mexico and other major trading partners are realized and business confidence falls as a result, global output could be about 0.5 percent below current projections by 2020.

In reflection of such negative sentiments, growth in trade of goods and services across the world was revised down 0.3 point from the April forecast to 4.8 percent in 2018 and 0.2 point to 4.5 percent in 2019, according to the IMF.

"Avoiding protectionist measures and finding a cooperative solution that promotes continued growth in goods and services trade remain essential to preserve the global expansion," the Washington-based institution said.

The IMF also cited faster-than-expected interest rate increases by the U.S. Federal Reserve and tighter global financial conditions as anther downside risk to world economic growth.

According to the report, the global growth projection was unchanged at 3.9 percent for next year. Similarly, the 2019 growth forecast was maintained at 2.7 percent for the United States, 6.4 percent for China and 0.9 percent for Japan.

The Japanese economy is expected to strengthen from the second to the final quarters of this year and into next year, bolstered by firmer private consumption, investment and external demand.

Weighed down by challenges such as migration policy and fiscal governance and uncertainty about Britain's planned exit from the European Union, the growth estimates for the 19-nation eurozone were revised down 0.2 point to 2.2 percent in 2018 and 0.1 point to 1.9 percent in 2019.