The $12bn San Francisco City & County Employees' Retirement System has invited tenders for a $636m global bond brief.

Brinson Partners, the US sister of London-based Phillips & Drew, together with Merrill Lynch Mercury Asset Management, currently manage portfolios of $401m and $235m respectively. Both have been invited to bid for the mandate - which could be split between more than one investment house, said Richard Piket, senior investment officer-fixed income.