By Ian Talley 

Six years after tackling the global financial crisis, the world's top economic policy makers are struggling to exit crisis-management mode and lift growth out of a long-term funk.

Troubles including low inflation, heavy debt loads, high unemployment and financial turmoil have dogged the global economy for years, keeping growth hovering at modest levels.

Those strains, including a potential default in Greece and emerging threats such as a deeper slowdown in China, are putting officials back on high alert as they brace for potential trouble.

The world's finance ministers and central bankers, who gathered in Washington through Sunday, sought to focus on hopeful signs such as lower oil prices supporting advanced economies, including the U.S. and Europe. But they noted that the world's overall growth outlook remains largely unchanged--3.5% this year--as many nations grapple with the legacies of the financial crisis.

"It's premature to talk about vibrant growth," said European Central Bank President Mario Draghi.

Despite a tone of increasing urgency, officials acknowledged they made little headway on an impasse over emergency financing for Greece. And while finance officials warned that currency volatility, low inflation and heavy debt levels threaten to undermine the uneven global economic recovery, they offered no consensus on how to fix the world's problems beyond more central-bank stimulus and calls for economic overhauls in individual nations to boost competitiveness.

International Monetary Fund Managing Director Christine Lagarde warned that inaction by policy makers around the world risks turning mediocre growth prospects into the new reality.

Many of the largest emerging markets are slowing or contracting, even before the potential shock waves expected if the Federal Reserve starts raising interest rates. Other risks--a potential Greek default and eurozone exit, financial bubbles, the Ukraine-Russia standoff and China's slowdown--are drawing increasing worry as policy makers hoped to build momentum for measures to finally boost global growth prospects.

"The world economy is not out of the woods," said Agustín Carstens, Mexico's central bank governor and chairman of the IMF's policy-setting committee. He said easy-money policies that policy makers backed to help pull the global economy out of the 2009 recession have led to more risk-taking in financial markets than in the real economy, an imbalance that made him uncomfortable.

The IMF has warned for years that countries must outline and deliver on major overhauls of their economies to spur growth.

"It's a recurring theme," said Mexico's finance minister, Luis Videgaray. "There's an overreliance in the world on monetary policy and perhaps not enough effort on the structural front."

Several efforts by the Group of 20 largest economies to spur growth have largely fallen by the wayside, victims of domestic politics that make passing economic overhauls much tougher. "The political processes required to address these issues are not simple," said Mr. Videgaray. "That's why monetary policy is bearing most of the burden."

Officials throughout their meetings tried to focus on the bright spots. The U.S. economy is gathering steam, albeit slowly. The eurozone is no longer flirting with recession. India's economy is now outpacing China as the world's fastest-growing emerging market. And cheaper oil prices could still goose growth in other major energy-importing countries.

But a host of threats are still worrying investors, economists and officials around the globe, keeping a lid on investment and dimming growth prospects.

Global economic growth is roughly in line with the average of the past three decades. That isn't strong enough to alleviate dangerously high debt levels and high unemployment in many countries. Meanwhile, potential growth--the ability of economies to expand based on the available labor supply, know-how and capital, is expected to fall through 2020, the IMF said.

Failure to enact longer-lasting structural overhauls after years of relying on central bank stimulus could stunt growth further.

"The risk is that we will get a little more growth, but not much more" through the ECB's efforts, said Italian Finance Minister Pier Carlo Padoan, whose government is gradually implementing a revamp of labor regulations, cutting taxes and other measures to increase competitiveness. "And we need more growth. Let's not forget that we have a huge unemployment problem."

Although the IMF says falling oil prices could create stronger-than-expected growth, it also warns the likelihood of a global recession had increased over the past six months.

Greece's worsening crisis is among the threats darkening the outlook. A standoff between Athens and its creditors over emergency financing is pushing the country perilously close to an exit from the eurozone, a prospect that could catapult the region back into financial and political turmoil.The eurozone has stronger defenses it can muster to counter a complete meltdown in Greece's economy than it did in 2012, the latest time the Mediterranean nation risked sending the region into a tailspin.

"Having said that, we're certainly entering into uncharted waters if the crisis were to precipitate," Mr. Draghi said on Saturday.

Diverging interest-rate policies, which are inciting currency volatility around the globe, also are worrying some officials. Investors are plowing their cash into the U.S. currency as the American economy strengthens and the Federal Reserve prepares to raise interest rates for the first time in nearly a decade. Combined with slowing growth in emerging markets and easy-money policies in the eurozone and Japan that depreciate the euro and the yen, demand for the dollar has sparked one of its strongest surges in decades.

Those competing pressures are spilling out across the globe. Officials from emerging markets said they were increasingly worried their economies could get whiplashed.

Jon Hilsenrath contributed to this article.

Write to Ian Talley at ian.talley@wsj.com