Tariffs imposed or threatened by the United States and China could shave 0.8 percent off global economic output in 2020 and trigger more losses in future years, the International Monetary Fund said on Thursday.

IMF spokesman Gerry Rice said trade tensions were beginning to affect a world economy already facing challenges including a weakening of manufacturing activity not seen since the global financial crisis of 2007-2008.

Rice told a regularly scheduled IMF news conference that the global lender is to release a new revised economic outlook next month, but provided no details.

World economic activity remained subdued, with trade and geopolitical tensions causing uncertainty and eroding business confidence, investment and trade, he said.

"Trade tensions... are not only a threat, but are actually beginning to weigh down the dynamism in the global economy," he said, adding U.S.-China tariffs "could potentially reduce the level of global GDP by 0.8 percent in 2020, with additional losses in future years."

Skepticism over the end of trade war

Mark Hamrick, economic analyst at Bankrate, a New York-based consumer financial services company, said the new forecast reflected skepticism that Washington and Beijing would end the trade war.

"Trade tensions have only grown. There is no agreement that is in sight," Hamrick said, noting that growing concerns in the business sector were starting to bleed into consumer sentiment.

Hamrick said the IMF assessment could fuel concerns about a U.S. recession after 11 years of expansion. Economists polled by Bankrate see a 41 percent chance of a recession by the time of the November 2020 U.S. presidential election, he said.

Asked if the IMF anticipates a global recession, Rice said that was not in the fund's baseline at the moment.

"Let's not get ahead of ourselves. Let's wait and see," he said, noting the forthcoming world economic outlook would provide greater clarity. Rice stressed he was not hinting that the IMF planned to forecast a recession.

Some goodwill gestures 

On September 1, a fresh wave of tariffs were imposed on a portion of 300 billion U.S. dollars worth of Chinese goods to the U.S., which is a decision deviated from the consensus reached by both countries' leaders during the G20 Osaka meeting in June.

As a tit for tat, China imposed the first batch of retaliatory tariffs of either 10 or 5 percent on 75 billion U.S. dollars of U.S. goods, which went into effect the same day. 

However, both sides have recently showed good gestures to carry forward trade consultations in October. 

On Wednesday, China unveiled the first set of U.S. goods to be excluded from the first round of additional tariffs.

The second day, the U.S. decided to postpone an additional five percent tariffs on 250 billion U.S. dollars worth of Chinese imports from October 1 to 15.

(With input from Reuters)