Accelerating towards full ownership, Italian carmaker Fiat is to buy another 3.3 percent of Chrysler, the US carmaker it manages. By exercising an option to purchase the shares owned by VEBA - a union healthcare trust fund - Fiat boosts its stake in Chrysler to 61.8 percent. Chrysler has helped Fiat offset weak car sales in Europe and increased its earnings in recent quarters. Fiat holds options to purchase up to 40 percent of Chrysler owned by VEBA, or the Voluntary Employees Beneficiary Association, which can be exercised until end-June 2016. At the same time the group announced Fiat-Chrysler sales in the US in June increased by 20 percent over the same period last year. In all 144,081 cars were sold, its best June total since 2007. More about: Car industry, Chrysler, Fiat