Athens, Jul 16 (IANS): Greek Prime Minister Alexis Tsipras on Wednesday called on his radical left Syriza party parliamentary group to remain united in critical times for the country, amid a string of anti-austerity strikes and protests.

The Greek leader addressed Syriza lawmakers in a closed-door meeting a few hours before a crucial vote scheduled for Wednesday midnight in the Greek parliament on the ratification of the debt deal reached with creditors in Brussels, Xinhua reported.

Tsipras earlier acknowledged that the agreement outlining a third bailout for Greece had tough terms, but insisted it was the only way to avert further default and a Grexit.

He called on Syriza ministers and lawmakers who voiced strong objections to the deal to submit "credible alternative solutions," Greek national news agency AMNA reported.

Energy Minister Panagiotis Lafazanis, who heads a group of hardliners within Syriza, has openly suggested a return to the drachma, rejecting Monday's agreement as humiliating and catastrophic. He is among quite a few prominent party members and ministers who have announced their intention to vote against the bill without clarifying in most cases whether they will also resign and hand over their seats.

Deputy Finance Minister Nadia Valavani was the first to formally submit her resignation from the ministry and parliament on Wednesday, denouncing the debt deal as "unsustainable".

Parliament Speaker Zoe Konstantopoulou also denounced the lenders' "blackmail" methods.

Tsipras and the ruling two-partite coalition face a critical test on Wednesday night. According to Greek media reports, about 30 Syriza deputies may vote against the debt deal and the first set of taxation and pension system reforms.

Syriza holds 149 seats in the 300-member chamber. Junior coalition partners, the right-wing Independent Greeks who have also raised questions over the final draft deal, hold another 13 seats. Both parties came to power six months ago on a strict anti- bailout and anti-austerity agenda.

Regardless of the dissent within Syriza, the draft bill is expected to be approved with the support of the opposition pro-euro parties.

The country is in arrears to the International Monetary Fund since July 1, while banks have been closed since June 29 and will remain shut until at least July 17, according to a new finance ministry announcement on Wednesday. Cash withdrawals from ATMs remain restricted to a daily 60 euros ($65.75) per debit card.

As Greek officials and lenders work to disburse emergency aid in the coming days to enable a loan repayment to the European Central Bank on July 20, the government also faces a wave of strikes and protests over the deal.

The public sector trade union ADEDY called a 24-hour strike on Wednesday, disrupting public transport for a few hours. They arranged for a demonstration in front of parliament on Syntagma square. Pharmacists joined in by shutting down pharmacies for the day while the Communist Party called for a similar rally in another central Athens square.