A senior European official says Greece has failed to reach a deal with bailout lenders before a May 1 target date set by Athens.

Negotiators from the International Monetary Fund and European Union institutions are in Athens to try and hammer out new austerity measures under a third international bailout, but failed late Tuesday to overcome differences.

Michel Reijns, a spokesman for Dutch Finance Minister Jeroen Dijsselbloem, wrote on Twitter that "more time needed" to reach agreement. Dijsselbloem chairs the group of eurozone finance ministers.

The delay is a setback for Greece's leftwing Prime Minister Alexis Tsipras who is seeking improved bailout repayment terms to try and revive the country's stagnant economy.

Greek state television reported Tsipras would request an emergency meeting of eurozone country leaders later this week.