DUBLIN — Italian unions geared for a strike against planned budget cuts Tuesday, and a core group of European finance ministers were expected to confer in Berlin, as officials struggled to halt a slow-motion crisis that is slamming world stock markets.

U.S. markets opened sharply down on Tuesday, with energy, tech and financials leading the sell-off. The Dow Jones Industrial Average fell 2.37 percent, the S&P 2.53 percent and Nasdaq 2.17 percent.

In Europe, exchanges were mixed, following a dramatic sell-off on Monday that pushed major indexes down more than 5 percent.

Asian exchanges fell Tuesday, some by more than 2 percent. Japan’s Nikkei closed at its lowest point since April 2009 — falling 2.2 percent, to a level unseen since the previous global economic downturn. Other major Asian markets also sustained losses, with South Korea’s KOSPI dropping 1.1 percent and Australia’s S&P/ASX 200 down 1.5 percent.

U.S. markets tumbled Friday, but were closed Monday for Labor Day.

In Switzerland, the National Bank surprised markets by slapping a new fixed minimum exchange rate of 1.20 francs to the euro. The Swiss have been struggling to curb their soaring currency, which has become a haven amid jitters over the euro. As a result, the nation’s exports are becoming increasingly expensive, threatening the Swiss economy.

Some analysts feared a disruption in currency markets if other nations that have also seen their currencies rise markedly as both the euro and the dollar have slumped consider similar measures.

The Swiss central bank warned it was prepared to buy massive amounts of foreign currency to support the new minimum exchange rate. The franc tumbled 9 percent against the euro and nearly 8 percent against the dollar in early trading.

Japan’s yen held steady against the dollar Tuesday, but it strengthened against the euro, hitting a six-month high of 108. Japan’s appreciating currency, particularly against the dollar, has hounded major exporters whose products become more expensive when the yen soars.

Tokyo last month attempted to intervene in its currency, but the impact was short-lived, and some financial analysts predict that the yen will rise to 73 or 72 against the dollar within several months.

With signs of an economic slowdown in the developed world, an increasing number of officials and analysts warn that Europe’s struggle over public debt and a weakened banking system could cause even broader problems.

Attention Tuesday was focused on Rome and Berlin. The Italian parliament was expected to begin debating a new austerity program of tax increases and budget cuts, and unions planned to strike in opposition.

In Berlin, the German, Finnish and Dutch finance ministers were slated to meet in an effort to resolve a disagreement that threatens to undermine an expanded bail-out for Greece. Finland wants collateral for its portion of any new emergency loan to Greece. Now other countries are calling for similar treatment. Germany opposes the idea and is trying to broker an alternative.

Fears about the world’s financial system have rekindled in recent days, with investors seeing little evidence that Europe has the ability, or political willingness, to stem the debt problems of some of its major economies. Borrowing costs for Italy and Spain rose on Monday. Runaway debts in several countries, notably Greece, pose the possibility of a major bank failure — the fallout from which would ripple through the international system.

In Japan, the Nikkei Tuesday sustained its third consecutive negative day, closing at 8590.57, below the lows it recorded in the days after the March 11 earthquake and nuclear disaster. As recently as Aug. 1, the Nikkei was above the key 10000 benchmark.

An economic downturn in areas that account for much of the world’s trade would be damaging on its own. But a full-blown financial crisis in Europe could have a devastating impact on both sides of the Atlantic.

The financial systems of Europe and the United States are closely intertwined, in ways that would make a major bank failure or loss of confidence in one area ripple through the entire system. The costs that banks pay to fund their businesses would rise, for example, and lending would slow. Related institutions could fail as well, because of the complex web of investments that major financial companies often share.

“In a pattern echoing that of the 2007-09 financial crisis, there is a growing risk of the real economy and financial conditions being locked into a mutually reinforcing downward spiral,” the Institute of International Finance wrote in a paper.

Politically, the signals also were bad. Borrowing costs for Italy jumped Monday as the government there stumbled over how to deliver promised deficit cuts, raising the prospect of what many in Europe consider a doomsday scenario: Italy’s trillions of dollars in outstanding bonds at risk of default, pushing the country toward a bailout that would strain the area’s political and financial capacity.

A defeat Sunday for German Chancellor Angela Merkel’s party emphasized the problems she may have in persuading Parliament to approve new German-funded support for other European governments.

A steady stream of recent data has pointed to a slowdown among the developed economies. Euro-area growth all but stopped during the past three months — including in Germany, the region’s economic powerhouse — and a report Friday showed no growth in U.S. employment in August.

In a recent analysis of how a financial crisis in one country can extend across borders, the International Monetary Fund said that the threatened collapse of a major European bank would produce a 40 percent probability of similar problems in a U.S. institution — similar to the stress seen during the crisis that followed the collapse of Lehman Brothers in 2008.

Harlan reported from Tokyo and Faiola reported from London.