Tsipras told the two leaders that the lenders' proposal could not be a basis for a deal because it was not taking into account the progress made in talks in Brussels over the past months, the official said adding that there was optimism that a deal could be reached soon.
Tsipras, elected in January on a promise to end austerity, returned from late night talks with EU officials in Brussels to face an outcry over conditions that would breach the "red lines" his Syriza party has declared.
He told ministers the government could not accept "extreme proposals" and said the creditors should understand that the Greek people had suffered enough and they "have to stop playing games at its expense", a Greek official said.
"They have not made any step back, regardless of the convergence reached during these four months on reforms that the Greek side included in its proposals but the lenders draft proposal did not," the official said on condition of anonymity.
Tsipras is due to brief parliament on the negotiations from 1500 GMT on Friday.
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Earlier the novice prime minister left the talks with European Commission President Jean-Claude Juncker and the chairman of euro zone finance ministers, Jeroen Dijsselbloem saying a deal with lenders was "within sight" and that Athens would make a 300 million euro payment to the IMF on Friday. His tone appeared to harden after he ran into a backlash in Athens.
European officials continued to voice optimism that an agreement could be clinched in the coming days, but they acknowledged that large gaps remained to be bridged and said they expected Greek counter-proposals.
Tsipras rejected pension cuts and a tax rise on electricity that he said the lenders were demanding along with other conditions to win the release frozen loans and avert a default that could hit euro zone and world markets.
Sources familiar with the creditors' five-page plan said it also asked Athens to commit to selling off state assets and maintaining unpopular labour reforms, demands that would cross the party's declared red lines.
The lenders were demanding that Greece reduce spending on pensions by 1.0 percentage point of gross domestic product and raise a further 1.0 percent or 1.8 billion euros ($2 billion) by increasing value-added tax on products ranging from drugs to electricity, the sources told Reuters.
Merkel, the EU's most influential leader, said the end was not yet in sight in the talks, telling a news conference: "The talks are far from reaching a conclusion."
She has tried to force the pace this week, at least partly to avoid a Group of Seven summit she will host in Bavaria from Sunday turning into another crisis session on the euro zone, highlighting Europe's difficulty in solving its own problems.
Her spokesman said Tsipras would not be invited to the G7.
Dijsselbloem said the Brussels talks that ran beyond midnight had narrowed down the remaining issues but differences were "still quite large" and Athens was expected to present alternatives to some of the lenders' proposals within days.