Athens: The leader of the leftist Syriza formation, Alexis Tsipras, took office on Monday as Greece's new prime minister after declining to swear the traditional oath before god and vowing to uphold the constitution to President Károlos Papulias.

After the ceremony, Tsipras and Papulias signed the decree that will pave the way for Tsipras to become Greece's youngest-ever head of government after his victory in Sunday's snap elections.

Papulias was given assurances by Tsirpas that the right-wing nationalist party, Independent Greeks, had pledged to support him in the upcoming parliamentary confidence vote after Syriza came up two deputies short of an absolute majority of 151 deputies in Sunday's polls.

Independent Greeks obtained 13 deputies Sunday.

"The required absolute majority exists and we therefore are in a position to form a government," Tsipras said but confided to Papulias he was convinced the majority would "grow some more" during the parliament's vote of confidence.

Before vowing in his oath to "work hard for the well-being of the Greek people," Tsipras paid a call on the Archbishop Hieronymous of Athens.

"I went there to assure him Church-State relations will be even more important that they have been in the past," Tsipras stressed.

"It will be dialogue and the best kind of cooperation possible that will bring us the best results," the Syriza leader added.