Christine Lagarde, Managing Director of the International Monetary Fund, has urged policy makers to use the window of opportunity offered by recent policy decisions.

Ms Lagarde also encouraged policy makers to take the actions needed to achieve a decisive turn in the global crisis.

"This time, we need a sustained rebound, not a bounce. If this time is to be different, we need certainty, not uncertainty. 

"We need decision makers to be real action takers. We need delivery," she said in a speech at the Peterson Institute for International Economics.

She described recent initiatives by major central banks as "big policy signals in the right direction" the European Central Bank's OMT bond-purchasing program, QE3 by the US Federal Reserve, and the Bank of Japan's expanded Asset Purchase Program.

At the same time, Ms Lagarde warned that the global economy is still fraught with risks and policy uncertainty is weighing growth down. The IMF continues to project a gradual recovery, but global growth will likely be a bit weaker than anticipated even in July, she said.

Speaking ahead of the joint Annual Meetings of the IMF and World Bank Boards of Governors in Tokyo, Ms Lagarde focused on three key sets of policy challenges: the unfinished agenda for Europe and the United States; increased pressures in the rest of the world; and commitments on which the IMF also must deliver.

"Europe obviously remains the epicenter of the crisis and where the most urgent action is needed," she said, calling on European policymakers to deliver on their commitments, including by establishing a single supervisory banking mechanism and enabling the direct recapitalization of banks.

Other actions include implementing the European financial firewall, notably the European Stability Mechanism; the agreed plan for fiscal union; and, at the country level, the reforms that are essential for growth, jobs, and competitiveness.

Ms Lagarde said that another major risk to the global economy is in the US, where current law implies a dramatic tightening of the deficit by about 4% of GDP next year. Failure to reach a deal on raising the debt ceiling could also force a dramatic tightening.

She called for action to avoid this so-called "fiscal cliff" and a concrete plan to bring down debt gradually over the medium term.

She also noted how, after leading the global economy in the current recovery, the major emerging markets are now slowing; she urged them to focus on countering vulnerabilities, whether domestic or external.