The worst debt-market slump in seven months is starting to disrupt bond sales by risky companies as investors retreat from funds that buy the debt.

Construction company Tutor Perini Corp. pulled a $500 million speculative-grade bond offering because of "adverse market conditions," it said in a statement late Wednesday. That left Wall Street underwriters without a junk-rated sale for the second day this week as anxiety about Tuesday's U.S. presidential election and a possible interest-rate hike next month by the Federal Reserve gripped capital markets.

Yields on high-yield bonds jumped for six straight days to 6.5 percent on Thursday — their highest in three months, according to Bloomberg Barclays index data. Borrowing costs were at their 2016 low of 5.98 percent just last week, the data show, as junk bonds headed for their best returns since 2009.