Athens - Greek lawmakers reacted angrily on Tuesday to concessions Athens offered in debt talks and parliament's deputy speaker warned the proposals might be rejected, puncturing optimism that a deal to pull Greece back from the abyss might be sealed quickly.
Euro zone leaders welcomed new budget proposals from Athens on Monday as a basis for further negotiations to unlock billions of euros in frozen aid and avert a default next week that could lead to a Greek exit from the single currency area.
Stock markets also cheered, with European shares extending the previous session's sharp rally and climbing to a three-week high on hopes of a deal. But the euro fell on fears the plan would struggle to win approval in the Greek parliament.
Prime Minister Alexis Tsipras, who was voted into office in January on a pledge to roll back years of austerity in a country battered by recession, must keep his leftist Syriza party as well as his creditors onside for a deal to stick.
Outspoken Syriza lawmakers voiced outrage at Tsipras's offer to raise a range of taxes as well as pension and healthcare contributions, which threaten to further increase hardship on Greeks reeling from previous rounds of austerity. One lawmaker said the deal was tantamount to a "tombstone" for Greece.
"I believe that this programme as we see it ... is difficult to pass by us," deputy parliament speaker and Syriza lawmaker Alexis Mitropoulos told Greek Mega TV.
"The prime minister first has to inform our people on why we failed in the negotiation and ended up with this result," he said. "I believe (the measures) are not in line with the principles of the left. This social carnage ... they cannot accept it."
Officials of the three institutions representing Athens' creditors - the European Commission, the European Central Bank and the International Monetary Fund - were analysing the Greek proposals intensively in Brussels to see whether the numbers add up to make Greek public finances sustainable.
The creditors may well come back and demand further savings, tax rises or reform measures in the drive to clinch a deal on Wednesday evening, when eurozone finance ministers meet at 17:00 GMT to review the outcome of the talks, people familiar with the situation said.
Comments by German Vice-Chancellor Sigmar Gabriel, warning Greece that its creditors would not be blackmailed, underscored that progress on a deal remained fragile. A European Commission spokesman emphasised that Greece needed to spell out what actions it will take before any bailout funds can be released.
If the Greek parliament fails to back a deal, Tsipras might be forced to call a snap election or a referendum that would prolong the uncertainty.