The third round of inter-Palestinian dialogue, mainly between rival Fatah and Islamic Hamas movement started on Wednesday in Cairo to resolve substantial differences, officials said.

The round of talks began on Wednesday morning in Cairo with bilateral meetings between the two rival groups' leaders, and in case they would overcome differences, other factions' leaders will join later.

Ismail Radwan, a senior Hamas leader said in a statement that the basic outstanding issues in the dialogue are related to the political platform of the unity government, the elections' system, and the security forces.

"I can assure that Hamas is going this time to the dialogue with open minds and hearts," Radwan said earlier in a statement sent to reporters. "The dialogue will be first between Fatah and Hamas, then the other factions will follow."

Hamas and Fatah delegations had arrived in Cairo Tuesday to resume a dialogue that lasted for ten days and ended on March 20 after disagreements on substantial issues. The two groups' leaders went for consultation with their leadership in both Gaza, Ramallah in the West Bank and Syria.

"We are serious in this dialogue and we are keen to achieve a national unity. We really hope that through this round of dialogue we will be able to reach a Palestinian-Palestinian agreement that empowers our unity," said Radwan.

He added that "any unity agreement should keep in consideration the legal armed resistance against the occupation and the basic Palestinian political principles related the legitimate rights of our people."

Radwan revealed that his movement's delegation, chaired by Musa Abu Marzooq, deputy of Hamas politburo, held talks late on Tuesday night with senior Egyptian intelligence officials to prepare for the third round of dialogue.

Fatah delegation, headed by senior Fatah leader Ahmed Qureia has also arrived in Cairo to resume the inter-reconciliation dialogue that leads to forming a unity government and ends the current status of rift.

Nabil Shaath, a senior Fatah leader said "the dialogue will resume to discuss the outstanding issues," adding "forming a unity government is still unresolved waiting for intelligence chief Omer Suleiman's return from the U.S."

"The idea was to find an exit to the problem of forming a new unity government that abides by the commitments and the agreements signed by Palestine Liberation Organization (PLO)," said Shaath.

The international Quartet, which imposed an embargo on former Hamas-led government, insists that any new unity Palestinian government should recognize Israel. Hamas still rejects the international requirements.