"We have an agreement on bridge financing.... This agreement is backed by the 28 member states," Commission Vice President Valdis Dombrovskis told reporters.
Greece must pay the European Central Bank a huge debt payment of 4.2 billion euros as early as Monday, and is in arrears to the IMF.
The bridging loan allows Greece to clear its debt to the IMF and to repay the ECB while the modalities of a fresh bailout, agreed in principal by European leaders on Monday, is still under negotiation.
The loan will be given through the EFSM, a rescue fund set up at the time of Greece's first bailout in 2010 but that involves the whole of the 28-nation EU, not just the 19 eurozone members.
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The loan will officially be for three months, but only provide enough cash to hold Greece over until August 20, when the country owes the ECB another huge debt payment.
Prime Minister David Cameron of non-euro Britain had insisted that his country would not be responsible for bailing out Greece, echoing comments by finance minister George Osborne who said the plan was a "complete non-starter".
The use of the EFSM risked causing a headache for Cameron as he seeks to renegotiate Britain's membership of the EU ahead of an in-out referendum by 2017.