Ismail Haniyeh, prime minister of Hamas in Gaza, on Saturday accepted Iran’s invitation to the Non-Aligned Movement summit in Tehran next week, according to an AFP report.

Earlier on Saturday, Palestinian Authority Prime Minister Salam Fayyad called on Haniyeh not to accept the invitation, saying his attendance would be a stab in the back for Palestinian national unity.

Haniyeh was invited to the conference by Iran on Friday.

Fayyad condemned Iran’s invitation and said the Islamic Republic was “against Palestinian national unity,” Israel Radio reported. He said the PA is the “sole and legitimate representative” of the Palestinian people, including Hamas, and that Haniyeh’s attendance would be a “stab in the back” for national reconciliation. It would delegitimize Palestinian unity efforts — just as Israeli Foreign Minister Avigdor Liberman’s recent letter denouncing and calling for the ouster of PA President Mahmoud Abbas had tried to do, he added.

The PA’s Foreign Affairs Minister Riyad al-Maliki also denounced Iran’s invitation of Haniyeh. He said that Abbas would not attend the conference if Haniyeh goes. “There is no need to invite other leaders [other than Abbas]” because the PA is the only legitimate Palestinian representative, he added.

Should he participate, Haniyeh would join UN Secretary-General Ban Ki-moon and the leaders of 118 other non-aligned states for the 16th triennial event from August 29-31.

Ban’s acceptance of Iran’s invitation on Wednesday earned the criticism of the United States and Israel. State Department spokeswoman Victoria Nuland reiterated after Ban’s acceptance the US’s “concerns that Iran is going to manipulate this opportunity and the attendees, to try to deflect attention from its own failings.”

Prime Minister Benjamin Netanyahu on August 12 urged Ban in a phone call not to attend – and, in a rare diplomatic breach, made the plea public.

“Even if it is not your intention, your visit will grant legitimacy to a regime that is the greatest threat to world peace and security,” Netanyahu told Ban in the phone call, according to a statement from the prime minister’s office.

The US, EU, Canada, Israel and other countries designate Hamas as a terrorist organization. It came to power in Gaza in 2007 after national elections followed by the violent overthrow of Abbas’s Fatah from Gaza.