The United States praised Israel on Thursday for showing "great restraint" in the face of new rocket attacks from the Palestinian group Hamas but added that Israel also has a right to defend itself.

Israel Air Force strikes on Thursday destroyed a Hamas security headquarters and a car carrying one of the group's top commanders. Israel had threatened a "severe" response to cross-border rocket attacks that have persisted despite a troop and settler pullout from Gaza in 2005.

State Department spokesman Sean McCormack urged restraint on all sides but said Israel had the right to respond to rocket attacks from Hamas, which he blamed for the latest upsurge in Palestinian violence.

"Israel has the right to defend itself and it has exercised great restraint in the face of these rocket attacks," McCormack told reporters.

U.S. Secretary of State Condoleezza Rice spoke earlier to Palestinian Authority Chairman Mahmoud Abbas as well as Prime Minister Ehud Olmert about the latest violence.

"She wanted to talk to them directly and see how they saw the situation," said McCormack. "We certainly want to see a reduction or an end to the violence but let's remember how that violence started and it started with these Hamas-led forces."

The current round of fighting began last Friday between rival Palestinian factions Hamas and Abbas's Fatah. More than 40 Palestinians have been killed in the most serious violence since the two groups formed a unity government in March.

At a news conference with British Prime Minister Tony Blair, U.S. President George W. Bush expressed concern over the violence in Gaza.

"We strongly urge the parties to work toward a two-state solution. Looking forward to continuing to work on this issue," he said.

"I've instructed my secretary of state to be actively engaged," Bush added.

"We understand the fright that can come when you're worried about a rocket landing on top of your home," he added.

Rice has sought in recent months to revive stalled peace efforts between the Palestinians and the Israelis, visiting the region almost monthly to try and bring the two sides together.

Asked how the latest violence affected her ability to continue this mission, McCormack said the United States remained "deeply engaged" and Rice planned to visit the region in the near future. He did not provide a date.

British Foreign Secretary Margaret Beckett released an official statement Thursday saying "I remain deeply worried by the continuing violence between militias in the Gaza Strip. We want to see the latest cease-fire take hold, for the sake of all the people of Gaza. I support President Abbas' efforts to achieve this."

"I also deplore rocket attacks from Gaza against Israel, attacks that are bringing suffering to Israeli civilians."

"I would like to express my sorrow for the families of civilians killed and injured, on all sides. I call on all parties to refrain from violence and to restore to the people of Gaza and nearby Israeli communities the security that they need and deserve."

Likud Chairman Benjamin Netanyahu on Thursday called on the government to cut off the power and water supplies in the Gaza Strip in a controlled fashion.

The opposition leader added that he supports a limited ground incursion into the Qassam firing area, roughly four kilometers past the border.

Speaking from the Menachem Begin Heritage Center in Jerusalem, where the Likud party was marking the 30th anniversary of the party's first elections victory, Netanyahu said that the paralysis and helplessness of the government "must leave this world".

"The government isn't doing anything," Netanyahu said, "Begin understood that the government's top priority was the lives of its citizens. This government doesn't realize that it must stop the methodical bombing of citizens' homes."

"Everyone must imagine what would happen if his house was hit by a Qassam," he added.

While Netanyahu was addressing his fellow Likud members in Jerusalem, Foreign Minister Tzipi Livni spoke with German Foreign Minister Frank Steinmeyer.

Livni said that if the international community does not put an end to the Qassam firings, Israel will be forced to do so.

The foreign minister added that she expects that the European Union to be involved in diplomatic efforts, condemn the Qassam firings and identify with the residents of Sderot.