(Bloomberg News) High-yield bond funds in the U.S. attracted $597 million from European investors last week, the most since February, as the region's leaders struggled to resolve the sovereign debt-crisis.

Inflows from Europe into U.S. speculative-grade funds in the period ended Aug. 22 doubled from $297 million in the previous week, according to data from research firm EPFR Global in Cambridge, Massachusetts. That's the most since $955 million of inflows in the week ended Feb. 8.

Investors are seeking haven in American junk bonds as the European Central Bank's plan to purchase government debt is said to be held up by a German court's ruling on a permanent bailout fund. ECB President Mario Draghi said he's waiting to unveil details of his plan until a Sept. 12 decision from Germany's Federal Constitutional Court.

"Last week, European investors pretty aggressively went hunting for higher yields," said Cameron Brandt, director of research at EPFR.

High-yield, high-risk, or junk, bonds are rated below Baa3 by Moody's Investors Service and lower than BBB- at Standard & Poor's.