Secretary of State Hillary Clinton will leave Asia on Tuesday to visit Israel, Egypt and Ramallah, stepping up U.S. efforts to avoid a worsening of the Gaza crisis, an official said.

Clinton will meet Israeli Prime Minister Benjamin Netanyahu and discuss the crisis with Egyptian and Palestinian leaders, after leaving President Barack Obama's trip to Southeast Asia, said senior Obama aide Ben Rhodes.

At least 20 Palestinians were killed on Tuesday as Israeli air strikes rocked the Gaza Strip, medics in the Hamas-ruled territory said, as a rocket fired by Palestinian militants exploded near Jerusalem.

Two cameramen from Hamas-owned Al-Aqsa TV were among six people killed in a series of Israeli air raids on Gaza City and the north, a Hamas spokesman said.

U.N. chief Ban Ki-moon on Tuesday urged all sides to the Gaza conflict to immediately cease their fire, warning at a news conference in Cairo that an escalation will endanger the whole region.

"All sides must halt fire immediately," Ban said, as an Israeli military operation against rocket-firing militants in Gaza entered a seventh day, with 116 Palestinians and three Israelis killed.

Israel's President Shimon Peres accused Iran Monday of encouraging the Palestinians to continue rocket attacks on Israel rather than negotiating a ceasefire, saying "they are out of their mind."

At the same time, Peres praised Egypt's President Mohammed Morsi for the constructive role he has played in the intensifying crisis.

The U.N. Security Council hit deadlock Monday on a statement on the Gaza conflict with the United States saying it opposes any action that undermines efforts to reach a ceasefire.

But Russia warned that unless an Arab-proposed statement calling for Israel-Hamas hostilities to end was agreed by Tuesday morning it would press for a vote on the full council resolution -- setting up a potential veto clash with the United States.

Protesters in Egypt's capital clashed with police on Monday during a protest to mark a year since a five-day long street battle with security forces in which dozens of protesters were killed, witnesses said.

The clashes erupted when demonstrators tried to destroy a concrete barrier security forces had put up to end last year's fighting with activists who wanted the military rulers at the time to transfer power to a civilian government.

European Union foreign ministers, in a new blow to President Bashar Assad's regime, on Monday said they viewed Syria's just-formed National Coalition to be the "legitimate representatives" of the Syrian people.

A statement from the bloc's 27 ministers welcomed the November 11 formation of the National Coalition for Syrian Revolutionary and Opposition Forces and said: "The EU considers them legitimate representatives of the aspirations of the Syrian people."

U.N. leader Ban Ki-moon arrived in Cairo on Monday to bolster Egypt-mediated efforts for a ceasefire in Gaza which officials said could end the conflict before it worsens with a possible Israeli ground invasion.

Ban will inject heavyweight impetus into the peace effort, meeting Foreign Minister Mohammed Kamel Amr and Arab League chief Nabil al-Arabi before flying to see Israeli Prime Minister Benjamin Netanyahu and Palestinian chief Mahmoud Abbas.

A newly formed Syrian opposition bloc that has received Arab and international backing is to be based in Egypt, its head Ahmed Moaz al-Khatib told the official MENA news agency on Monday.

"It has been decided that the Syrian National Coalition will have its headquarters in Egypt," Khatib was quoted as saying after talks with Egyptian Foreign Minister Mohammed Kamel Amr.

The newly formed Syrian opposition coalition is likely to get an offering of support from the European Union on Monday, an EU official said, in what would be a significant vote of confidence for a movement struggling to prove its credibility and gain the trust of the country's factions.

Such a move would not amount to official diplomatic recognition because that can only be decided by each EU country individually. But if the bloc's 27 foreign ministers meeting in Brussels decide that the coalition is a legitimate voice for Syria's people it would be a major step forward in the West's acceptance of the group.