Israel did not seek approval from Washington before waging a ground invasion into the Gaza Strip ruled by the Islamic Resistance Movement (Hamas), said US Vice President Dick Cheney on Sunday.

"They didn't seek clearance or approval from us, certainly," the vice president said on CBS' Face The Nation on Sunday, his first public remark on Israel's military strikes targeted Hamas.

Israel's ground troops, backed by gunships and tanks, on Saturday night launched an invasion into the Gaza Strip. Reports here quoted Palestinian security sources as saying that the troops have gained control of the eastern section of the northern Gaza Strip throughout Sunday.

The strikes lasting eight days in the Gaza Strip have killed some 480 people, mostly Palestinian militants, and wounded 2,800 others. For the Israeli side, four people have been killed in the ongoing rocket attacks by Hamas and other Palestinian militants from the Gaza Strip.

"I think it's important to remember who the enemy is here," Cheney said, when asked if the ground attack was a mistake. "The enemy is not the Palestinians, from the perspective of the Israelis -- it's Hamas ... You've got a UN member state being attacked by a terrorist organization."

"To go after that terrorist organization, I think they probably decided that an air campaign wasn't enough, that they had to go in on the ground if they were going to take down the sites from which the rockets had been launched against Israel," Cheney defended Israel's ground operation.

"If there's to be a ceasefire, you can't simply go back to the status quo anti, what it was a few weeks ago. ... It's got to be a sustainable, durable proposition, and Hamas has to stop rocketing Israel. And I don't think you can have a viable ceasefire until they prepare to do that," said Cheney.

(Xinhua News Agency January 5, 2009)