Liberty Mutual Group Inc. issued $750 million of bonds to help finance a payment to a unit of Warren Buffett’s Berkshire Hathaway Inc. for covering the insurance company’s liabilities tied to asbestos.

The 4.85 percent, 30-year notes were sold to yield 160 basis points more than similar-maturity Treasuries, according to data compiled by Bloomberg. Standard & Poor’s increased Liberty Mutual’s rating one level to BBB from BBB- after Berkshire’s National Indemnity Co. agreed last week to provide as much as $6.5 billion of coverage for the insurance company’s liabilities for asbestos, environmental and workers compensation policies.

“This agreement covers Liberty Mutual’s potentially volatile U.S. A&E liabilities and largely mitigates potential risks from future adverse reserve developments,” Tracy Dolin, an S&P analyst, said in a statement.

Berkshire, which has grown over the last five decades by investing insurance premiums in stocks and takeovers, has assumed billions of dollars in asbestos risk from insurers including American International Group Inc. and CNA Financial Corp.

Liberty Mutual paid Omaha, Neb.-based National Indemnity about $3 billion for the coverage, according to a July 17 company statement.

“This agreement further strengthens our financial position as it eliminates a substantial source of uncertainty in these liabilities,” Liberty Mutual Chief Executive Officer David H. Long said in the statement.

The bond sale will be Liberty Mutual’s first since October, when the Boston-based company issued $400 million of 4.25 percent notes due 2023 that yielded 170 basis points more than benchmarks, Bloomberg data show. A basis point is 0.01 percentage point.

—With assistance from Noah Buhayar in New York.