Lagarde, in separate statements late on Wednesday, singled out Switzerland and Poland for increasing their contributions, hailing their "enduring support for the spirit of multilateralism."
"Ensuring the Fund has sufficient resources to tackle crises and to promote global economic stability is in the interests of all our members," she said.
The IMF statement said "Switzerland and other countries" had pledged $26 billion of increased funding while Poland had agreed to provide $8 billion.
"This brings to about $320 billion the commitments received so far. I am, (of) course, very encouraged by this strong demonstration of support for the Fund, and I look forward to further commitments from our broader membership."
In a Frankfurt Allgemeine Zeitung interview published this week, Lagarde revealed that the International Monetary Fund is seeking some $400 billion for expanding its crisis intervention "firepower."
That was sharply lower than the original target of $500 billion. Last week Lagarde said the Fund was lowering its target, citing a slight easing of financial tensions, both globally and in the eurozone.
The largest contributions thus far have come from the eurozone, which has pledged some $200 billion, and Japan, which pledged $60 billion.
The IMF is hoping to firm up more commitments, especially from the big emerging economies like China, Russia, Brazil and India, at the Fund's spring meetings held at the end of this week in Washington.