BMO Capital Markets says that it’s only a matter of time before the U.S. central bank pulls the trigger on some further monetary easing measures.

In a speech Friday, Ben Bernanke, chairman of the U.S. Federal Reserve Board, spelled out the policy options the Fed has left, with key lending rates already at rock bottom levels. The various unconventional measures he discussed include quantitative easing, conditional commitments to low rates, and lowering rates on excess reserves.

In that speech, Bernanke “reordered the arrows in the Fed’s policy quiver” says BMO in a research note. Markets had wondered if lowering rates on excess reserves would be its next move, but it now appears that further quantitative easing or credit easing would be its first choice, BMO suggests.

“The order of preference emphasizes how much more risky the economic situation must have become in Bernanke’s mind. If the Fed has to act again, they want something that is sure to work, despite the potential costs,” it says.

“The Fed’s talk and walk is now all about convincing us not to adopt a deflation mentality,” BMO adds. But, if deflation does start to seem like a real possibility, the Fed will throw everything is has at the problem, BMO says.

“While Bernanke was specific about the Fed’s policy options, there was conditionality in his tone. He is prepared to deploy them, but is still not convinced that he will have to,” BMO concludes. “Although the economic data have been bad of late, they are going to have to get worse before the next policy arrow gets fired. In our view, it’s only a matter of time.”