ATHENS, Greece (AP) — Greece's prime minister on Wednesday raised the political stakes ahead of next month's early national election, saying he will not enter a coalition with the main center-right and centrist opposition parties even if he needs their backing to govern.

Alexis Tsipras resigned last week, barely seven months into his four-year mandate, when his bailout-dependent country received a new rescue loan that saved it from a looming bankruptcy and exit from the euro currency.

He is seeking a stronger mandate, after his radical left-led coalition effectively lost its parliamentary majority when dozens of his own hardline left lawmakers refused to back new austerity measures demanded for the loan — which parliament approved with the backing of pro-European opposition parties.

Tsipras is widely expected to win the snap election, which will most likely be held Sept. 20, but it is unclear whether he will secure enough seats in parliament to govern alone.

In an interview with private Alpha TV Wednesday, Tsipras ruled out a coalition with the center-right main opposition New Democracy party, or the smaller centrist Potami and PASOK parties.

"I will not become prime minister in a coalition government with (New Democracy, PASOK or Potami)," he said. "I think that all three parties essentially express the old political system."

Before the election date is set, main opposition parties must complete the formal process of trying to form a national unity government. That procedure — doomed due to the parties' disagreements — is expected to end Thursday.

Tsipras' disaffected former comrades are angry at his policy U-turn to secure the international loans, as he was elected Jan. 25 on pledges to scrap creditor-demanded income cuts and tax hikes. They have formed the rebel group Popular Unity, now Greece's third-largest party.

Deepening the rift in Syriza, 53 members of the 201-strong central committee — the main party organ — announced their resignations from the party Wednesday, as they are switching to Popular Unity.

Tsipras has argued that he was forced to accept creditors' terms to keep Greece in the euro, and said that if he secures a slender majority in the election he will seek a coalition with his current partner, the small right wing populist Independent Greeks.

But polls show that the Independent Greeks might not make it into parliament, which would greatly compromise Tsipras' position: He cannot form a coalition with the politically toxic Nazi-inspired Golden Dawn, Greece's fourth-strongest party, the anti-European Communist Party or Popular Unity.

Economist Intelligence Unit analyst Joan Hoey said Wednesday that the snap elections will not bring Greece political stability, and formation of Popular Unity will likely cost Tsipras a majority.

"The election is likely to result in the formation of another Syriza-led government coalition that is just as unstable as the outgoing one," she said.

"The new government will encounter growing popular opposition to new austerity and reform measures," she said. "(We) put the chances of a Greek exit from the euro zone at 60 percent over the next five years."

In his interview, Tsipras said he accepted the bailout deal to avoid having to deal with a Greek bank collapse "and, possibly, civil strife" if the country was forced out of the euro.

Tsipras also explained why, shortly before the agreement, he sacked his flamboyant finance minister, Yanis Varoufakis, who alienated Greece's creditors in the European Commission, International Monetary Fund and European Central Bank with his aggressive talk and delaying tactics.

Tsipras said that in a top-level June 25 meeting he and Varoufakis attended with the IMF, ECB and EC heads, "(Varoufakis) was talking and they paid no attention to him. They had switched off," Tsipras said. "He had lost his credibility with his interlocutors."