Bank of America Corp is considering further paring its stake in China Construction Bank Corp, just weeks after it sold a big chunk of the mainland lender. Officials of the US bank contacted Construction Bank at the weekend to say it is weighing selling some of its shares in the mainland lender to boost its capital, according to people familiar with the matter. The US bank has been a shareholder of Construction Bank since 2005, when it was a so-called cornerstone investor at the time the mainland bank listed on the Hong Kong stock exchange. Construction Bank is the mainland's second-biggest lender by market capitalisation. In August, Bank of America announced that it was selling half its 10 per cent stake in Construction Bank, or 13.1 billion H shares, in a private transaction with a group of investors to raise capital. That was the end of a contractual period during which the US bank could not divest its stake. The sale generated about US$8.3 billion and an after-tax gain of about US$3.3 billion. Bank of America said at the time that it would be left with about 5 per cent of the mainland lender. It said their partnership had been 'mutually beneficial' and that they were 'discussing a potential expansion and extension of the existing strategic assistance agreement'. Based on Friday's close of HK$5.82, Bank of America's holding of 12.5 billion Construction Bank shares is worth about HK$73 billion. However, two billion shares were restricted from being sold until 2013, said Michael Werner, a senior analyst at Sanford C. Bernstein. If Bank of America sold all but the restricted shares, its holding in the mainland bank would fall to 0.83 per cent from 5.21 per cent, Werner said. Both banks declined to comment. Further divesting its Construction Bank stake would fit with other moves the US bank is making to shore up its capital base. In a filing with the US Securities and Exchange Commission last week, Bank of America said it was looking at issuing up to 400 million shares to boost its capital. The plan marks an about-face for the bank, which had maintained that it would not issue shares that would dilute existing shareholdings. Regulators are calling for banks around the world to increase their capital so they can better withstand economic shocks. From 2013, banks will have to increase their capital under Basel III rules. In addition, 29 of the world's biggest banks deemed to be globally systemically important, including Bank of America and Bank of China, will be subject to an additional capital surcharge from 2016, according to a list announced on Friday by the Group of 20 nations. Jefferson Harralson, a managing director at Keefe, Bruyette & Woods Financial Institutions Research, said while other banks might be better off due to Basel III's long phase-in period - until 2019 - Bank of America faced a potential equity shortage. As part of its efforts to boost capital adequacy levels, Bank of America has been divesting non-core assets. It sold its holdings in several companies last year, including asset management firm BlackRock and Spanish bank Banco Santander. Construction Bank's shares came under pressure before Bank of America's sell-off in August. According to a source close to the situation, the State Administration of Foreign Exchange, which manages most of the mainland's US$3.2 trillion in foreign reserves, the National Social Security Fund, Citic Securities and Temasek Holdings, Singapore's sovereign wealth fund, were among the buyers of Bank of America's Construction Bank shares.