...The vote laid bare the anger within Tsipras’s leftist Syriza party at the austerity measures and reforms which he accepted in exchange for the bailout loans. Altogether 43 lawmakers – or nearly a third of Syriza deputies – voted against or abstained.

The unexpectedly large contingent of dissenters, including former finance minister Yanis Varoufakis, heaped pressure on Tsipras to clear the rebels swiftly from his party and call early elections in the hope of locking in popular support.

Tsipras remains hugely popular in Greece for trying to stand up to Germany’s insistence on austerity before relenting under the threat of a euro zone exit. He would be expected to win again if snap polls were held now, given an opposition that is in disarray.

“I do not regret my decision to compromise,” Tsipras said in parliament as he defended the bailout from euro zone and International Monetary Fund creditors. “We undertook the responsibility to stay alive over choosing suicide.”

But the vote left the government with support from within its own coalition below the threshold of 120 votes in the 300-seat chamber, the minimum needed to command a majority and survive a confidence vote if others abstain.

In response, government officials said Tsipras was expected to call a confidence vote in parliament after Greece makes a debt payment to the European Central Bank on Aug. 20 – a move that could trigger the government’s collapse and snap elections.

A senior lawmaker, Makis Voridis, from the opposition New Democracy said his party would vote against Tsipras’s coalition, raising the odds it would be toppled....