U.S. stocks fell Tuesday, tracking Asia and Europe, while crude oil remained weak amid worries about global economic growth.

Christine Lagarde, head of the International Monetary Fund, warned in a speech in Frankfurt, Germany, that the global economy’s recovery “remains too slow” and “too fragile.” Although Lagarde cited “much progress since the great financial crisis,” her comments added to concern that the IMF may revise down its forecasts for global growth. “Let me be clear: We are on alert, not alarm,” she said. “There has been a loss of growth momentum.”

U.S. markets opened on a downswing that carried the day. The Dow Jones industrial average was off 0.8 percent by the close of trading, the tech-heavy Nasdaq composite finished down 1 percent and the Standard & Poor’s 500-stock index dropped 1 percent. The yield on a 10-year U.S. Treasury bond slipped to 1.7 percent, its lowest point since mid-February.

Pharmaceutical company Allergan was among the biggest losers, with its share price plunging as much as 21 percent in the wake of new Treasury Department rules cracking down on tax inversions — schemes in which U.S. firms are bought by foreign companies in a bid to lower their tax burdens. The rules could derail its $160 billion merger with Pfizer — indeed, CNBC, citing people familiar with the matter, reported late Tuesday that the companies were abandoning the merger. In regular trading before that report, Allergan’s stock was down 15 percent; Pfizer was up 2.6 percent.

Also Tuesday, the government reported that the gap between U.S. imports and exports rose 2.6 percent to $47.1 billion in February — a wider than expected gulf.

In Europe, the Stoxx Europe 600 fell to its lowest point since mid-February, while Germany’s DAX index dropped more than 2.6 percent after new data showed a decline in manufacturing orders.

In Asia, Japan’s Nikkei closed down 2.4 percent while the yen hit a 17-month high vs. the dollar.

West Texas Intermediate crude posted a modest gain Tuesday but remains below its rebound peaks in mid-March.

The WTI price dropped 3 percent Monday over worries that a proposed global deal to freeze oil production may fall through. Concerns about a glut drove that benchmark down to just over $26 a barrel in February and roiled global financial markets. That unrest was eased when oil ministers from Russia and Saudi Arabia said they would freeze production at current high levels — but with a caveat that only if Iran would, too.

Over the weekend, an Iranian official said the country will ramp up its oil production until it reaches the market share it had secured before international sanctions — leaving investors skeptical that the deal will come together at a meeting of the world’s top oil producers in Doha on April 17.