Blackstone Group LP, the world’s biggest private-equity firm, is in talks to buy a stake in Goldman Sachs Group Inc.’s European insurance business, according to a person with direct knowledge of the matter.

The price and size of the stake to be acquired by Blackstone’s Tactical Opportunities fund are being discussed, and a deal still may not be reached, said the person, who requested anonymity because the negotiations are private. The companies were considering the sale of a minority stake, the Financial Times reported Aug. 16, citing people familiar with the matter.

Goldman Sachs, which said it probably will sell a majority of London-based Rothesay Life Ltd., is doing so in part because new rules require banks to hold more equity to absorb potential losses on assets, a person briefed on the discussions said earlier this month. The business, run by Goldman Sachs partner Addy Loudiadis, 50, insures more than 10 billion pounds ($15.6 billion) of pension liabilities for companies including IAG SA’s British Airways.

Christine Anderson, a spokeswoman for New York-based Blackstone, and Michael DuVally at Goldman Sachs declined to comment on the potential deal.

The Tactical Opportunities fund, which oversaw $2.7 billion as of April, invests across Blackstone’s four main strategies: private equity, real estate, credit and hedge funds. It’s led by David Blitzer, 43, a senior managing director who started the firm’s European private-equity business in 2002.

Basel Rules

Rothesay, which Goldman Sachs set up in 2007, had $9.66 billion of assets at the end of the second quarter, an Aug. 8 filing shows. The unit had a pretax operating profit of 266 million pounds in 2012, according to its website.

Goldman Sachs’s Tier 1 common equity was equal to 9.3 percent of the bank’s risk-weighted assets at the end of June under new rules from the Basel Committee on Banking Supervision known as Basel III, according to the filing. The New York-based bank has said it wants to maintain a ratio of about 9.5 percent, or 1 percentage point higher than regulators will require.

The firm’s Tier 1 common equity was reduced by $9.87 billion because of investments in non-consolidated financial institutions, according to the filing. That brought its Basel III figure to $55.8 billion, compared with $61.9 billion under current rules.

Insurance Insider reported earlier that Goldman Sachs and Blackstone were discussing a deal.

With assistance from Donal Griffin in New York. Editors: David Scheer, Greg Storey