Palestinian president Mahmoud Abbas will boycott the Non-Aligned Movement summit in Iran if his Islamist rival Ismail Haniya of Hamas attends, a minister told Agence France Presse on Saturday.
"President Abbas will not take part in the Non-Aligned summit if Haniya is present, no matter what form his attendance takes," foreign minister Riyad al-Malki said in Ramallah, headquarters of the Palestinian Authority.
A Hamas spokesman earlier on Saturday said Haniya would attend the August 30-31 conference in Tehran "in accordance with the invitation from Iranian President Mahmoud Ahmadinejad."
The statement from Taher al-Nunu, a spokesman for the Hamas government in the Gaza Strip, did not say when Haniya would leave the Palestinian enclave for the conference or give any further details.
In Iran, foreign ministry spokesman Rahmin Mehmanparast said Haniya had been invited to the gathering as a "special guest."
Abbas heads a rival West Bank-based administration, and said last month that he had accepted an invitation to attend the NAM summit and make his first visit to the Islamic republic.
"At a time when (Israeli Foreign Minister Avigdor) Lieberman is waging an aggressive political campaign, the invitation to Haniya to attend the NAM summit indicates that Tehran has joined the hostile Israeli chorus," the Palestine Liberation Organization executive committee said in a statement.
On Thursday, Lieberman said Abbas was waging a form of "diplomatic terror" against Israel that was as dangerous as the violent threat posed by Hamas.
It was his second personal attack on Abbas in as many days and came after he called for world powers to force Palestinian elections in a bid to replace him.
"The aim of all this is to strike a blow against the Palestinian national struggle by encouraging division and giving him recognition and legitimacy," the PLO statement added in reference to Iranian policies on Hamas.
Iran is a backer of Hamas which has long been in conflict with Abbas's secular Fatah, and the Palestinian president has accused Tehran of trying to stymie attempts between the factions to reconcile.
In April 2011, Abbas's Fatah and Hamas announced a surprise reconciliation and agreed on the creation of an interim cabinet of independents selected by the two factions, to prepare for elections to take place by May 2012.
But the deal has largely stalled, leaving presidential and legislative elections indefinitely postponed, although the Abbas administration has called for local authority polls in the West Bank in October.
Palestinian Prime Minister Salam Fayyad also criticized Iran's invitation to Haniya, calling it a "serious escalation" against Palestinian unity.
Tehran has sparked a fresh wave of outrage in Israel after Ahmadinejad and Iran's supreme leader Ayatollah Ali Khamenei both described the Jewish state as a "cancerous tumor."
Mehmanparast has called the NAM meeting "the greatest political summit in Iran's history."
The United Nations has said Secretary General Ban Ki-moon will attend the summit, despite protests by Israel and calls from the United States to stay away, and will be in Tehran from August 29 to August 31.