MEMPHIS, Tennessee -- It was reported this week that International Paper Co. tapped the bond markets on Tuesday to help pay down its pension obligation. The company joins General Motors Co., which took similar steps in February, in taking advantage of low borrowing rates to cope with a surge in corporate pension liabilities.

Memphis, Tenn.-based International Paper borrowed $2.3 billion in bond markets, and will use $500 million of that to fund contributions to its pension plan, according to a company press release. International Paper had a pension benefit obligation of $4.2 billion at the end of June, and has taken several steps this year to reduce the burden. It contributed $250 million to the plan in the first half of the year, and paid $1.2 billion to employees as part of a voluntary buyout plan during the second quarter.

Falling interest rates have caused pension obligations to rise this year. Under accounting rules, declining rates trigger an increase in pension liabilities. The combined pension deficit for S&P 1500 companies ballooned to $568 billion at the end of June, a $164 billion increase from the end of 2015, according to Mercer, a benefits consulting firm.

In February, General Motors Co. sold $2 billion of bonds, and pumped the money into its pension plan. One investment banker at a major bank said he expects similar deals to come to market as the year progresses.