GAZA (Reuters) - Islamic Jihad said on Thursday it would not formally sign on to an Egyptian-brokered truce with Israel but would not be the first to violate it.

Citing an unnamed high-level Egyptian official, Egypt's state news agency MENA said on Wednesday that Palestinian factions meeting in Cairo had agreed to an Egyptian proposal for a truce with Israel starting in the Hamas-controlled Gaza Strip.

But a number of factions were equivocal in their support for a ceasefire, and some said they reserved the right to retaliate against Israeli attacks.

In a new statement, Zeyad al-Nakhala, deputy to exiled Islamic Jihad chief Ramadan Shallah, said the group could not be a party to a truce agreement that did not also apply at the onset to the occupied West Bank.

"But we will not be the first to violate or undermine it, and we will give a chance for the reopening of (the Gaza Strip's border) crossings and alleviating the suffering of our people," Nakhala said.

MENA said Cairo's proposal was part of a broader plan eventually leading to the lifting of Gaza border restrictions which Israel, with Egyptian help, tightened after Hamas Islamists seized the territory last June.

Islamic Jihad militants in the Gaza Strip have been behind numerous rocket attacks on Israel, strikes which the group and other Palestinian factions say are in response to Israeli military operations in the territory.

Israel, which pulled troops and settlers from the Gaza Strip in 2005 but still controls its frontiers, has said it would have no reason to launch attacks in the coastal enclave if Palestinians halted their rocket fire.

(Writing by Jeffrey Heller in Jerusalem, Reporting by Nidal al-Mughrabi in Gaza and Aziz El-Kaissouni in Cairo, Editing by Stephen Weeks)