Palestinian President Mahmoud Abbas's Fatah group threatened on Wednesday to arrest Hamas members if the Islamist movement banned Gaza Fatah delegates from attending a congress in the West Bank.

Hamas, which controls the Gaza Strip, has conditioned the departure of some 400 Fatah members for the long-delayed Fatah meeting in Bethlehem on Aug. 4 on the release of hundreds of Hamas activists detained by Palestinian forces in the West Bank.

Hamas also wants more passports issued from the West Bank, where Abbas holds a sway, for its officials and supporters in the Gaza Strip.

Abbas has said he would cancel Fatah's first congress in 20 years if Gaza members were banned from attending. "If they do not allow Fatah members to leave Gaza, we will arrest their men here," said a senior Fatah official in the West Bank, who declined to be identified.

On Sunday, Hamas prevented three Fatah members from leaving the Gaza Strip, which fell under Hamas control after the group routed forces loyal to Abbas in a brief civil war in 2007.

"A ban of our men will be the last nail in the coffin of (Fatah-Hamas) dialogue," said Raed Radwan, a Fatah leader in the West Bank city of Ramallah, referring to Egyptian-sponsored talks that have failed to clinch a unity agreement.

Hamas leader Sami Abu Zuhri said Fatah threats "would not succeed" in changing its position.

Hamas and Fatah have been accusing each other of carrying out political arrests in the West Bank and Gaza Strip.

The secular Fatah movement, which dominated Palestinian politics for decades until it lost a 2006 election to Hamas, has spent some four years wrangling over convening the congress it hopes will set it on a path of reform and democratisation.

Fatah's last congress -- the fifth in the movement's 44-year history -- was held in 1989 in Tunisia. Abbas has asked Egypt and Syria to pressure Hamas to allow Fatah members to leave the Gaza Strip to attend the forum.

Hussein al-Sheikh, a Palestinian official liaising with Israel over the congress, said he had secured its agreement to allow Fatah members living abroad and in the Gaza Strip to enter the West Bank, territory captured by Israel in a 1967 war.