Hamas co-founded Mahmoud Zahar said Abbas “is not interested in achieving” a unity government - alleging this is because the US and Israel oppose it.
“Reconciliation will not be achieved at all,” Zahar told the London-based daily Asharq al-Awsat.
Abbas and Hamas chief Khaled Mashaal met last week to try to move ahead with a reconciliation deal they reached in in May.
It was their first serious face-to-face sitdown since Hamas broke a prior coalition government and seized Gaza from Fatah in a violent putsch in 2007.
After the Abbas and Mashaal hailed a "new era of cooperation," but observers noted no key points of division between the rival movements have been respolved.
Earlier this week, Abbas moved a step further, setting May 4 as the date for elections that are to be held as part of the reconciliation agreement.
However, it remains unclear whether Abbas is engaged in political maneuvering orserious about the deal, which could prompt a Western nations to cut foreign aid donations to Abbas' cash-strapped in Ramallah.
Israeli officials have warned a unity agreement with Hamas would be a death knell for the already comatose peace process.
Zahar, an infamous Hamas strongman and hardliner, was a key figure in the 2007 Gaza takeover. He was not part of the Hamas delegation of that accompanied Mashaal to Cairo for his meeting with Abbas last week.
Ahmed Assaf, a spokesman of Abbas’ Fatah movement, said Zahar’s comments reflect internal divisions in Hamas.
“President Abbas and the Fatah leadership are keen to end the split,” Assaf said. “We have the impression that the Hamas leadership is interested in that, too, despite some voices, like Zahar’s.”
Hamas maintains that "resistance" is the only path to statehood and that any peace agreement reached with Israel will only serve as a prelude to furthering its agenda of destroying the Jewish state.