In a speech at the Brookings Institution in Washington, he also decried currency manipulations by speculators and called for stricter global control of currency markets. The Greek government blames speculators for exacerbating the financial crisis and for weakening the euro.
"It is common sense, enforced by insurance regulators, that a person is not allowed to buy fire insurance on his neighbor's house and then burn it down to collect on that insurance," Papandreou said, comparing speculators to arsonists. "If Europe and America jointly step in to shore up global financial regulation, and to finally ensure enforcement of regulations, we can curtail such activities."
He encouraged U.S. authorities to continue investigations into possible currency manipulation involving the euro.
The International Monetary Fund says the lending institution is also planning informal meetings with Greek Finance Minister George Papaconstantinou, who is accompanying Papandreou.
Papandreou was not specific about what help he was seeking from Obama, but he emphasized that financial instability in Greece and Europe posed a threat to the United States. Papandreou has said his country is not looking for money from other governments, only help in securing loans at reasonable rates.
"For America, a weak euro means a rising dollar. That, in turn, means a rising U.S. trade deficit," he said. "If the EU -- still America's biggest trading partner -- should falter, the consequences here would be palpable.
Papandreou's trip to Washington is part of a four-country trip seeking firmer EU and U.S. support for new measures to rein in Greece's massive budget gap.
Greece has committed to a severe austerity plan to reduce its 12.7 percent budget deficit and has warned that going to the International Monetary Fund is an option if a European solution is not found. Such action would be embarrassing to Europe because it would suggest the EU is unable to deal with its own problems.