Disagreement within the Hamas leadership over a reconciliation deal signed by leaders of Hamas and the Palestinian Authority in Qatar is stalling the formation of a unity government, senior Fatah member Nabil Sha'ath said Monday.

Palestinian Authority President Mahmoud Abbas is waiting to hear confirmation from Hamas that they will stand behind an interim government under his premiership, Sha'ath told Palestinian news agency Ma'an.

Sha'ath made the comments as an open leadership split within Hamas - the first of its kind in the history of the Islamist movement - arose over how far it should go in closing ranks with Fatah. Hamas has been working with the PA to end a conflict with Fatah that erupted after Hamas won Palestinian elections in 2006, and forcefully ejected Fatah from the Gaza Strip the following year.

Some leaders in Hamas have said it would be illegal for Abbas to become prime minister of an interim government while he is still president, a part of the deal that Abbas and Hamas leader Khaled Mashaal signed in Doha. Sha'ath rejected such claims on Monday as untrue.

The senior Fatah leader - who has visited Gaza since the signing of a reconciliation agreement between the PA and Hamas in Cairo last May - said there is nothing in Palestinian law which prevents the president from appointing himself to the position of prime minister.

"The issue here is not constitutional," he said. "The solution is a political solution."

Sha'ath said he hoped that "Hamas does not make [the deal] an obstacle," adding that "we in Fatah will not use this as an excuse to stop working towards unity."

Sha'ath said Fatah would have "no role" in helping to solve what he called an "internal issue" within Hamas.