Sales of corporate bonds from the U.S. to Europe and Asia slumped to their lowest levels this year and borrowing costs soared to the most since February as a global slowdown curbed demand for all but the safest assets.

Deere & Co., the largest maker of agricultural equipment, and Springdale, Arkansas-based Tyson Foods Inc. led weekly sales of at least $39.5 billion, the smallest amount since the five days ended Dec. 30, according to data compiled by Bloomberg. Offerings fell below the 2012 weekly average of $76.8 billion for the fourth consecutive period as yields rose to 4.272 percent from the low this year of 4.06 percent on May 8.

High-yield issuance in the U.S. was virtually shut as Federal Reserve Chairman Ben S. Bernanke said the world's largest economy is threatened by Europe's debt crisis and government budget cuts, making it harder for corporate borrowers to meet their obligations. China reduced its benchmark interest rate for the first time since 2008, stepping up efforts to combat a deepening slowdown.