Defense Secretary Leon Panetta spoke with Israeli Defense Minister Ehud Barak this week about the latest Israeli military moves in Gaza after increased rocket attacks from there.
A senior U.S. defense official confirmed the conversation had taken place in the last few days while Panetta was traveling in Asia.
"They spoke about unacceptable attacks by Hamas and other groups in Gaza, and Panetta expressed the U.S. view that Israel has the right to defend itself," the official said.
Right now, the United States largely believes the situation will remain contained between Israel and Gaza, according to U.S. and Israeli officials CNN has spoken with.
There is a belief that Hamas will pull back its rocket attacks, avoiding a full-blown Israeli air and ground assault into Gaza.
Israeli forces are going after Hamas weapons and storage bunkers near the Israeli border as part of the attacks in Gaza, an Israeli official told CNN. Israel also expects to hit weapons labs and workshops, said the official, who has direct knowledge of Israeli plans but declined to be identified because of the sensitive nature of the information.
The Israeli army is moving nearly a division's worth of troops -- perhaps 1,500 to 2,000 -- to the border and will move into Gaza if Hamas continues its rocket attacks on Israel, he said, even as airstrikes already have begun. Further air and any ground operations, he said, would be against Hamas weapons and leadership.
Israel says it's been hit by 800 rockets fired from Gaza so far this year. The official said that's twice as many as were fired in 2011 and three times as many as in 2010.
Israel estimates there are still 12,000 rockets in Gaza and that 1.5 million Israelis are in striking range. Hamas, the Israeli official said, can strike as far as Tel Aviv with portions of its inventory. He said that Hamas elements in Gaza fired more than 100 rockets this week.