GAZA CITY (Reuters) -- The two top leaders of Hamas failed to resolve an internal crisis over a reconciliation pact with the rival Fatah movement of President Mahmoud Abbas at secret talks in Qatar on Sunday, a diplomat in the region said.

"(Hamas chief) Khalid Mashaal and (Gaza Premier) Ismail Haniyeh met last night in Qatar to discuss the dispute in Hamas over the Doha agreement," the diplomat told Reuters on Monday.

Mashaal has recently quit his longtime Damascus headquarters, politically embarrassed by Syrian President Bashar Assad's bloody crackdown on an uprising waged by fellow Sunni Muslims. Haniyeh flew to Qatar from Iran, Syria's ally and a sworn enemy of Israel and its Western supporters, which was displeased by Mashaal's refusal to stay and support Assad.

The two Islamist leaders are not, however, on opposing sides of the internal dispute in Hamas, but are trying to resolve differences in its collegial leadership between Mashaal and Gaza-based group leaders close to Haniyeh, analysts say.

"The crisis persists," the diplomat told Reuters after the Qatar meeting. He asked not to be identified.

Meanwhile, Fatah leader Nabil Shaath told Ma'an on Monday that the internal disagreement in Hamas was holding up the appointment of a unity government, after Mashaal agreed in Doha last week for Abbas to head the interim body.

Abbas is waiting for confirmation from Hamas that they will back the new cabinet, Shaath said.

He disputed the accusation from opponents of the deal that Abbas holding both posts of president and prime minister broke Palestinian law, noting that the persistence of divided Hamas and Fatah-led governments was itself unconstitutional.

"Abbas was only chosen after a number of candidates were rejected, particularly (current premier in the West Bank) Salam Fayyad," he added.

Internal split

Hamas and Fatah have been enemies since their armed factions fought in Gaza in 2007, splitting the Palestinian national movement in two.

Both movements have been saying for over a year that it is high time to end their divisive and damaging rivalry. But so far they have failed to make a deal that will stick.

Some in the top ranks of Hamas believe that with Middle East peace talks now on the rocks, the recent rise of Islamist movements in the Arab world gives them more leverage over Western-backed Abbas than they have ever had.

But Hamas leader-in-exile Mashaal, with close ties to Egypt's Muslim Brotherhood, sees it as a time for accommodation rather than confrontation, together with subtle policy adjustments to end Hamas's isolation.

Mashaal and Abbas signed a pact last week for Abbas to lead an interim government of technocrats with the task of preparing for overdue presidential and parliamentary elections later this year.

Haniyeh, the Hamas leader in Gaza, backed the deal but other senior Hamas figures in Gaza were vocally opposed, pitching the movement into a rare open dispute.

The Qatar deal angered those in Gaza who feel Meshaal made too big a concession to the Palestinian leader in the Israeli-occupied West Bank without obtaining their approval.

Under Hamas rule, Gaza effectively runs its own affairs, ignoring anything from the West Bank that it does not like.

Analysts say Hamas leaders in Gaza believe there is no need for concessions at this time to Western-backed Abbas, whose foreign-funded Palestinian Authority holds sway in the Israeli-occupied West Bank, separated from Gaza by Israeli territory.

Hamas formally opposes a permanent peace with Israel, and is shunned by the United Nations and the West as a terrorist organization.

Analysts say there is no indication whatever that Hamas is getting ready to change this policy, but they are intrigued by Mashaal's softer tone in recent months, and the suspicions it has aroused among Hamas hardliners.

'Tough dilemma'

Mahmoud Al-Zahar, a senior Hamas figure in Gaza seen as a hardliner by Fatah, described Mashaal's agreement with Abbas as a "mistake". Zahar clashed with Mashaal late last year when the exiled leader advocated giving Abbas more time to pursue his peacemaking with Israel.

"Gaza leaders believe they have the jurisdiction over Gaza where any agreement has to be implemented, while Mashaal believes he did what is best to end political rifts," said a second diplomat in the region.

"The group for the first time in its history finds itself in a real and tough dilemma," he said. "The Doha agreement needs a miracle to be implemented. The crack it caused in the integrity of Hamas is one that will be difficult to overcome."

Hamas sources say some officials are demanding that the group should have key portfolios in the proposed interim government if Abbas is to be prime minister as well as president.

That would appear to violate a key term of the deal, that the government must be made up of political independents, not politicians from the rival factions.