The US Federal Reserve goes into a key rate-setting meeting this week with markets expecting policymakers to pull the trigger on a rate hike to tackle persistently high inflation -- and analysts say central bank chief Kevin Warsh's credibility is on the line. In recent weeks, however, several Fed policymakers -- including Warsh himself -- have hinted that if inflation does not show clear signs of slowing, the central bank will have to act by raising interest rates.