German Chancellor Angela Merkel warned Greece Monday that it did not have much time left to secure a deal to unlock billions in rescue funds.

"There's not much time left. We have to work very hard on this," said Merkel at the close of the G7 leaders summit. Greece desperately needs to secure the release of 7.2 billion euros ($8 billion) in aid funds from its IMF and EU creditors in order to meet debt servicing payments totalling 1.6 billion euros by the end of June.