The worldwide finance agency dropped its projection for world economic growth by two-tenths of a percentage point for both 2018 and 2019 to 3.7 percent, the first time it had trimmed its economic outlook in more than two years.
According to the WEO report, growth is on the mend for sub-Saharan Africa, with the region's average growth projected to rise to 3.1 per cent in 2018 (from 2.7 per cent in 2017) and 3.8 per cent in 2019.
Prominent US academic Jeffrey Sachs was less diplomatic in his assessment of Trump's shepherding of American trade relationships, slamming the president's repeated claims that deficits with China and other nations meant Americans were being taken advantage of.
Growth is projected to slow to 6.6 percent this year and 6.2 percent in 2019, a downgrade of 0.2 percentage points.
A raising of United States interest rates has also helped send emerging market currencies into a tail spin, as countries that borrowed heavily in dollars race to pay back their debt.
The brighter outlook is due to higher non-oil growth and an uptick in oil production as global crude output cuts that started in January past year, come to an end.
"Uncertainty over trade policy is prominent in the wake of USA actions (or threatened actions) on several fronts, the responses by its trading partners, and a general weakening of multilateral consultation on trade issues", the report said.
The cut its 2019 USA growth forecast to 2.5 percent from 2.7 percent previously, while it reduced China's 2019 growth forecast to 6.2 percent from 6.4 percent.
"This is the biggest ever deficit of Pakistan's history", he said.
"U.S. growth will decline once parts of its fiscal stimulus go into reverse", International Monetary Fund chief economist Maurice Obstfeld said in a statement. "Notwithstanding the present demand momentum, we have downgraded our 2019 United States growth forecast owing to the recently enacted tariffs on a wide range of imports from China and China's retaliation." .
Further out, China's economy is expected to slow gradually to 5.6 percent as the government shifts to "a more sustainable growth path" and addresses financial risks, the International Monetary Fund said.
While the global economy is still on track to match last year's pace, which was the strongest since 2011, the new outlook suggests fatigue is setting in and the overall performance masked divergence with mounting weakness in emerging markets from Brazil to Turkey.
"In several key economies, moreover, growth is being supported by policies that seem unsustainable over the longer term".
He called on countries to ensure inclusive growth, which he said was "more important than ever".
Trump has repeatedly touted Wall Street records as proof of the success of his economic programme including his confrontational trade strategy, and has frequently criticised the Fed for gradually raising interest rates, which could press the brakes on equity markets.