Ukraine's three major parliamentary parties have agreed to form a new coalition on March 29 and nominate parliamentary speaker Volodymyr Hroysman to be Ukraine's new prime minister, party officials said.

The three new coalition partners include Ukrainian Prime Minister Arseniy Yatsenyuk's party, President Petro Poroshenko's faction, and former Prime Minister Yulia Tymoshenko's Fatherland party. All three were previously coalition partners.

Two former coalition allies -- the populist Radical party and the reformist Self-Help party -- have refused to rejoin the alliance, the party officials said late on March 28.

The deal could mark the end of months of political infighting and corruption allegations that have stymied reforms demanded by the West and derailed negotiations for a new $1.7 billion loan from the International Monetary Fund needed to prop up the struggling economy.

Maksym Burbak, the head of Yatsenyuk's People's Front party, announced the agreement after a meeting of deputies with Poroshenko and Yatsenyuk, and said a meeting to form the new coalition would begin at noon on March 29.

Oleh Lyashko, head of the Radical Party, said Hroysman would be named the coalition's candidate for prime minister at the meeting, and a vote on his nomination will take place in the evening.

Lyashko added that his party would not attend the noon meeting.

"So far, our initiatives have been ignored, so we don't see a possibility to take part in the new coalition," he said.

Representatives of Poroshenko's faction and the Fatherland party have not yet commented on the developments.

Support for Yatsenyuk has tumbled recently, but he has refused to step down until a new coalition agreement is signed.

The formation of the new coalition would improve the chances of Hroysman, a 38-year-old former mayor and ally of Poroshenko, of receiving parliamentary support for his nomination.

With reporting by Reuters and TASS