The Federal Reserve gave a rosier assessment of the US economy while reaffirming that it is in no hurry to increase interest rates. Janet Yellen is stepping up a debate over when to raise interest rates for the first time since 2006 as unemployment falls faster than expected and inflation picks up toward their 2% goal. Gross domestic product grew at a 4% annualised rate in the second quarter, well above the 3% rate that had been expected and a sharp reversal from the weather-impacted first quarter, when the economy contracted a revised 2.1%.