By Dena Aubin

NEW YORK, Jan 23 (Reuters) - U.S. junk bond sales have jumped 75 percent in January to $3.4 billion, a sign that riskier assets are joining in a general credit market thaw.

January's total is the highest since June, when $8.4 billion in high-yield bonds were sold, according to Thomson Reuters data. Just $1.9 billion were sold in January 2008.

Junk bonds have rallied since December as record high yields above 22 percent attracted cash into the market. Junk, or high-yield bonds, posted a 7.47 percent total return in December and have gained 4.66 percent in the month to date, according to Merrill Lynch data.

Low interest rates on safe-haven U.S. Treasuries and money market funds and last year's massive losses in equities have prompted investors to move cash into high-yield bonds, strategists said.

"Investors are increasingly recognizing the benefits of yield product," said Peter Toal, head of high-yield capital markets, Americas at Barclays Capital in New York. "Buying high-yield today with double-digit yields to some investors, can be pretty attractive when they're not earning anything in the money markets."

Junk bond sales evaporated late last year as the worst credit crisis in generations caused investors to shun risk. With many Wall Street dealers scrambling to curb their own risk exposure, the amount of junk bonds on dealers' inventories was also cut to the bare bones.

Now that the market is rallying, new issues are the only place many investors can find large blocks of bonds.

"If accounts have cash and want to put a meaningful amount to work, they're finding that opportunity in the new issue market," said Toal.