WASHINGTON—The global economy is increasingly vulnerable to a sharp slowdown as troubles in emerging markets mount and as advanced economies struggle to grow, the World Bank warned Tuesday.

The bank’s latest projection pegs global growth at 2.4%, down from the 2.9% forecast in January and slower than last year’s weak pace. The bank also cut its forecast for growth in 2017 to 2.8% from 3.1%.

“The global outlook faces pronounced risks of another stretch of muted growth,” said World Bank chief economist Kaushik Basu. “A wide range of risks threaten to derail the recovery.”

Commodity exporters such as Brazil, Russia, Nigeria and Angola suffered some of the largest downward revisions. Governments have been forced to cut spending due to the price collapse in metals, energy and other commodities. Weakening currencies also are forcing central banks to raise interest rates to curb rampant inflation. And higher borrowing costs are weighing on investment and putting many company balance sheets deep into the red.

The bank pared its projections for the world’s largest economy, the U.S. A wounded energy sector, strong dollar and anemic international demand contributed to a 0.8-percentage-point cut in growth expectations—to 1.9%—for the year.

Japan, the world’s third-largest economy, isn’t gaining traction despite the Bank of Japan ’s charge into negative-rate territory. The World Bank said Japan will grow by 0.5% this year, nearly a full percentage point lower than expected in January.

The bank fears emerging-market growth could decelerate further. The bank kept its forecast for a 6.7% expansion in China, the world’s No. 2 economy, as Beijing juices output with more stimulus. But the World Bank warned of building financial risks that could trigger a deep slide in growth.

Bank economists are also concerned the Federal Reserve could tighten faster than markets expect, causing a jump in borrowing costs that could spark financial turmoil around the world. Volatility in capital flows also could flare up again if jittery investors pull out of emerging-market equity, currency and bond markets, they said.

The economists cited political risks as a threat to future growth. A U.K. exit from the European Union could severely damp investment as uncertainty weighs on markets, they said.

In the U.S., many economists are also pointing to uncertainty in the presidential election as suppressing activity. Governments from Brazil to South Africa to Indonesia also are facing deepening political turbulence, on top of persistent risks from wars in the Middle East and geopolitical tensions in the South China Sea.

“If we have a major shock, it can translate into a very sharp slowdown for the global economy,” said Ayhan Kose, the chief author of the bank’s Global Economic Prospects report.

Policy makers’ room to maneuver is shrinking. Although debt levels have moderated in many advanced economies, central banks are starting to run out of monetary-policy options. And politicians are reluctant to use government balance sheets to fund major injections of stimulus.

Options are even fewer among emerging-market exporters. Debt levels are rising, budget deficits are deepening and central banks are having to raise rates instead of cutting them to temper rising prices as their currencies weaken. Those countries, such as Angola, Kazakhstan, Malaysia, South Africa and Venezuela, are running average budget deficits of 5% of gross domestic product.

One major indicator of global weakness—trade growth—remains muted at 3.1%, well below precrisis trends.

“Persistently low growth could intensify protectionist tendencies that would further weaken growth prospects,” the bank said.

That attitude can be seen in the antitrade rhetoric gathering strength in the U.S. presidential election, but it isn’t isolated to North America. Around the world, discriminatory practices that act as a barrier to international trade outpace liberalization efforts by more than two-to-one, the bank said.

One bright note in the outlook: Emerging-market importers aren’t suffering the same downturn as exporters. In countries such as India, Hungary, Thailand and Vietnam, government deficits are actually lower than the bank forecast two years ago and debt levels as a share of economic output are falling.