MILAN - IMF chief Christine Lagarde hopes to gain broad consensus on a more than $400 billion rise in the fund's firepower this week, an Italian newspaper on Tuesday quoted her as saying, though it may take some time to gain final commitments.

"I really hope this week we'll reach the critical mass of more than $400 billion. We are determined to do all we can," Christine Lagarde told financial daily Il Sole 24 Ore.

"I am ready to leave the matter open for a few weeks: some countries need a little bit more time for parliamentary approval," she added.

Lagarde reiterated her view that the increase needed in the IMF's firepower was now estimated to be smaller compared to when it was last assessed at end-December.

"The overall risk evaluation is unchanged, but we are in April and some countries have already raised on the markets more than half of what they need for 2012, so our estimate has shrunk."