A bond to raise money for life-saving vaccines in the world's poorest countries has been delayed after a choppy week for global bond investors, according to Reuters. Backed by six European countries, the bond was originally due to be launched on Thursday after investor presentations in Europe and the United States. No new date has been fixed and the offering is not expected for at least another week. The British Treasury said the delay was to allow for an extended investor roadshow and that the response to the deal had been strong. But many in the market suspected the postponement was due to difficult market conditions and a glut of competing new issues. Government bond prices have fallen in all major markets during the past week as nervousness over the global interest rate outlook has brought an abrupt end to a three-month rally. A rush of new government and corporate bond issues this week has also put upward pressure on bond yields, making it more expensive to raise funds. Investment banks Goldman Sachs and Deutsche Bank are managing the offering which is expected to raise up to $1 billion. Funds raised will support immunisation projects against diseases such as measles and polio in 70 of the world's poorest countries. "It's important to set a good benchmark and they're not going to be rushed," said one source close to the deal. The project is championed by British finance minister Gordon Brown who hopes it will be a pilot for a wider financing scheme that could double rich countries' development aid to $100 billion a year. The bond will be the first from the International Finance Facility for Immunisation, a specially-created body backed by Britain, France, Italy, Spain, Sweden and Norway. Brazil and South Africa have pledged to join at a later date.