UNITED NATIONS, April 29 (Reuters) - UN Secretary-General Ban Ki-moon on Friday cautiously welcomed a unity agreement aimed at ending the rivalry among ruling Palestinian factions, but stressed that it should not undermine peace with Israel.

The Secretary-General welcomes efforts being made to promote Palestinian reconciliation and the important contribution of Egypt in this regard, UN spokesman Martin Nesirky said in a statement.

He hopes that reconciliation will now take place in a manner that promotes the cause of peace, security and non-violence, he said.

The Egyptian-brokered deal, announced on Wednesday, calls for forming a new government acceptable to both Palestinian President Mahmoud Abbas's Fatah faction, which is dominant in the West Bank, and the Gaza Strip Hamas's rulers.

Egypt has invited Palestinian leaders to Cairo next week for the signing of the deal, Palestinian officials said on Friday.

Israel denounced the agreement, saying Abbas could not be a peace partner if he mends ties with Hamas, an Islamist group whose charter calls for the destruction of the Jewish state, but which has said it is open to a long-term ceasefire.

Nesirky indicated that Ban wanted Abbas' more moderate Fatah movement to lead any unity government.

The United Nations has long underscored the need for progress towards Palestinian unity within the framework of the Palestinian Authority led by President Abbas and the commitments of the Palestine Liberation Organization, he said.

The United Nations will study carefully the agreement as soon as the details are available, Nesirky added.

(Reporting by Louis Charbonneau; Editing by Will Dunham)