The Federal Reserve on Wednesday signalled that it still expected to keep interest rates near zero for at least six months, but for the first time identified factors that could lead to earlier rate rises.

In a shift foreshadowed in the Financial Times, the US central bank tweaked guidance in its policy statement that had been unchanged since March, edging away from a simple forecast that it expects to keep rates at “exceptionally low levels” for an “extended period” – commonly understood to mean at least six months.