U.S. Secretary of State Hillary Clinton met Israeli Prime Minister Benjamin Netanyahu on Tuesday and pledged to work for a truce in the Gaza Strip "in the days ahead."
As the two began late-night talks in Jerusalem, Palestinian rocket fire and Israeli air strikes continued. Netanyahu said he would prefer a "long-term" diplomatic solution but repeated his readiness to step up an offensive against Gaza's rocket crews.
Clinton's outline of further days of negotiation, notably in Cairo with Egyptian President Mohamed Mursi, may dampen talk of an immediate end to a week of violence that has killed over 140 people, most Palestinians but including two Israelis on Tuesday.
Officials from Egypt and from Gaza's ruling Hamas movement had talked up the chances of an end to hostilities, at least in some interim form, by the end of the day. But a Hamas leader in Cairo later told Reuters there would be no announcement before Wednesday. He blamed Israel for not responding to proposals.
Netanyahu, who faces a general election in two months and had mobilized army reserves for threatened ground invasion of the enclave, stressed his interest in a "long-term" deal to end rocket fire on Israel - a kind of deal that has eluded him and his predecessors in four years since Israel's last offensive.
Clinton, too, who broke off from an Asian tour with President Barack Obama and assured Netanyahu of "rock-solid" U.S. support for Israel's security, spoke of seeking a "durable outcome" and of the "responsibility" for contributing to peace borne by Egypt, Gaza's other neighbor, whose new leaders hail from the Muslim Brotherhood that inspired Hamas's founders.
"In the days ahead, the United States will work with our partners here in Israel and across the region toward an outcome that bolsters security for the people of Israel, improves conditions for the people of Gaza and moves toward a comprehensive peace for all people of the region," Clinton said.
"It is essential to de-escalate the situation in Gaza. The rocket attacks from terrorist organizations inside Gaza on Israeli cities and towns must end and a broader calm restored.
"The goal must be a durable outcome that promotes regional stability and advances the security and legitimate aspirations of Israelis and Palestinians alike."
Netanyahu, who has seemed in no immediate rush to repeat the invasion of winter 2008-09 in which over 1,400 Palestinians died, said: "If there is a possibility of achieving a long-term solution to this problem with diplomatic means, we prefer that.
"But if not, I'm sure you understand that Israel will have to take whatever action is necessary to defend its people."
The Jewish state launched the campaign last week with the declared aim of halting the rocketing of its towns from the Palestinian enclave, ruled by the Hamas militant group that does not recognize Israel's right to exist.
Medical officials in Gaza said 31 Palestinians were killed on Tuesday. An Israeli soldier and a civilian died when rockets exploded near the Gaza frontier, police and the army said.
Gaza medical officials say 138 people have died in Israeli strikes, mostly civilians, including 34 children. In all, five Israelis have died, including three civilians killed last week.
Khaled Meshaal, exile leader of Hamas, said on Monday that Israel must halt its military action and lift its blockade of the Palestinian coastal enclave in exchange for a truce.
Obama, whose relations with the hawkish Netanyahu have long been strained, has said he want a diplomatic solution, rather than a possible Israeli ground operation in the densely populated territory, home to 1.7 million Palestinians.
Israel's military on Tuesday targeted more than 130 sites in Gaza, including ammunition stores and the Gaza headquarters of the National Islamic Bank. Israeli police said more than 150 rockets were fired from Gaza by the evening.
"No country would tolerate rocket attacks against its cities and against its civilians. Israel cannot tolerate such attacks," Netanyahu said with U.N. Secretary-General Ban Ki-moon, who arrived in Jerusalem from talks in Cairo, at his side.
After nightfall, Israel stepped up its Gaza bombardment. Artillery shells and missiles fired from naval gunboats slammed into the territory and air strikes came at a frequency of about one every 10 minutes.
In an attack claimed in Gaza by Hamas's armed wing, a longer-range rocket targeted Jerusalem on Tuesday for the second time since Israel launched the air offensive.
The rocket, which fell harmlessly in the occupied West Bank, triggered warning sirens in the holy city about the time Ban arrived for truce discussions. Another rocket damaged an apartment building in Rishon Lezion, near Tel Aviv.
Rockets fired at the two big cities over the past week were the first to reach them in decades, a sign of what Israel says is an increasing threat from Gaza militants.
In the Gaza Strip on Tuesday, Hamas executed six alleged collaborators, whom a security source quoted by the Hamas Aqsa radio said "were caught red-handed" with "filming equipment to take footage of positions". The radio said they were shot.
Militants on a motorcycle dragged the body of one of the men through the streets.
Along Israel's sandy, fenced-off border with the Gaza Strip, tanks, artillery and infantry massed in field encampments awaiting any orders to go in. Some 45,000 reserve troops have been called up since the offensive was launched.
A delegation of nine Arab ministers, led by the Egyptian foreign minister, visited Gaza in a further signal of heightened Arab solidarity with the Palestinians.
Egypt has been a key player in efforts to end the most serious fighting between Israel and Palestinian militants since a three-week Israeli invasion of the enclave in the winter of 2008-09. Egypt has a 1979 peace treaty with Israel seen by the West as the cornerstone of Middle East peace, but that has been tested as never before by the removal of U.S. ally Hosni Mubarak as president last year in the Arab Spring uprisings.
Mursi, elected Egyptian president this year, is a veteran of the Muslim Brotherhood, spiritual mentors of Hamas, but says he is committed to Egypt's treaty with Israel.
Mursi has warned Netanyahu of serious consequences from an invasion of the kind into Gaza four years ago. But he has been careful so far not to alienate Israel, or Washington, a major aid donor to Egypt.
Additional reporting by Cairo bureau; Writing by Jeffrey Heller and Alastair Macdonald; Editing by Alison Williams