Global growth in 2019 should be even slower than previously expected but a "precarious" rebound later this year is likely.

The world economy was vulnerable to shocks from Brexit, high debt levels and trade tensions, as well as unease on financial markets

"The expected rebound in global growth this year is precarious”. "This is a delicate moment that requires us to handle with care."

The IMF next week was due to cut its global growth forecasts even further than it had in January, with more than two thirds of the world economy likely to see slowing growth.

Gloom about slowing growth in Asia, Europe and the United States, as well as the protected US-China trade war, have sparked periodic jitters on markets since last year.

At the start of the year, the fund had already lowered its expectations several notches from a prior outlook, calling for global GDP to expand by 3.5 percent this year and next.

"We had this synchronized acceleration of growth a couple of years ago. Now it's synchronized deceleration," Lagarde said following her speech. "I don't want to be overly dramatic, because we don't see a recession."

But Lagarde pointed to some grounds for optimism, saying major central banks, including the US Federal Reserve, were showing patience about the speed of interest rate increases, while China had moved to stimulate its economy.

She called on member governments to help avert mounting dangers by modernizing tax systems, cutting public debts and reducing wealth inequalities through spending on education, health and infrastructure, recommendations the IMF has made before.

Lagarde repeated warnings about imposing tariffs, saying such barriers to trade were "potentially self-inflicted wounds" that threatened to dent economic growth and leave no winners.

Lagarde also said new IMF research showed that an all-out trade war between the United States and China -- with 25 per cent duties on all traded merchandise -- could shave up to 1.6 per cent off of annual growth in China and 0.6 per cent off US GDP growth.

While there were signs of progress in talks between the United States and China, a deal should be "signed, sealed and delivered" before it can restore certainty to global trade.