Treasury's Lew fears miscalculation over Greece could spark new crisis
"The challenge for the Europeans, the political and economic institutions -- the IMF -- is to show enough flexibility," Lew said at the London School of Economics.
"So if the Greeks are prepared to take the kinds of tough steps that they need to take, they find a pathway to resolving this without there being an unnecessary crisis."
(Reporting by David Milliken and Jemima Kelly, writing by Andy Bruce; editing by John Stonestreet)