Defense Secretary Leon E. Panetta said Sunday that he did not think Israel had yet made a decision to strike Iran, but that his goal in meeting with the Israeli leadership this week was to strengthen ties with the United States “so that we can be fully prepared to deal with any contingency that may happen.”

Mr. Panetta made his comments to reporters on his plane as he headed to Tunis, Tunisia’s capital, the first stop on a five-day trip to North Africa and the Middle East. He is to meet on Tuesday and Wednesday in Jerusalem with Prime Minister Benjamin Netanyahu and Defense Minister Ehud Barak.

Mr. Panetta sidestepped questions on whether he would urge Israel not to attack Iran, as Obama administration officials have privately counseled Israel over many months. He instead cast the Obama administration’s consultations with Israel over how to stop Iran’s nuclear program as close and unified.

They are, at the very least, frequent: Mr. Panetta is the most recent in a parade of administration officials to visit Israel in the past three weeks, among them Secretary of State Hillary Rodham Clinton; Thomas E. Donilon, the national security adviser; John O. Brennan, the counterterrorism chief; and assorted officials from the State Department, Pentagon and White House.

The visits have effectively served to sandwich in Mitt Romney, the presumptive Republican presidential nominee, who was in Jerusalem on Sunday, two and a half weeks after Mrs. Clinton, five days after Mr. Brennan and two days before Mr. Panetta.

On Israel, Mr. Panetta said, “My view is that they have not made any decisions with regards to Iran, and they continue to support the international effort to bring pressure against Iran to pull back from their efforts to develop their nuclear capability.”

He declared that Israel and the international community were united in the view that economic sanctions on Iran were effective, and he declined to comment on Mr. Netanyahu’s remarks on Sunday to Mr. Romney that the sanctions were not working.

Mr. Panetta also declined to comment on a remark by Dan Senor, a senior adviser to Mr. Romney, that if Israel acted against Iran on its own, Mr. Romney “would respect that decision.”

“I’m just not going to get into that game of commenting on what candidates do,” Mr. Panetta said. “As secretary of defense, I have a responsibility to defend the security of our country, and in order to do that I have to have the support of both Democrats and Republicans.”

He did acknowledge Israel’s right to act on its own. “We respect their sovereignty and their ability to make decisions with their own security,” he said, repeating a standard administration stance. But he did not tie the administration’s respect for Israel’s sovereignty directly to a possible Israeli attack on Iran.

On Syria, Mr. Panetta told reporters that helicopter gunship attacks on civilians in the city of Aleppo by President Bashar al-Assad’s government were “another tragic example of the kind of indiscriminate violence that the Assad regime has committed against its own people” and that “it ultimately will be a nail in Assad’s coffin.” He offered no details, but said the United States was working with countries in the region to try to secure Syria’s large stockpiles of chemical and biological weapons. The Obama administration says it is not providing direct military aid to the Syrian opposition.

In Tunisia — where the Arab Spring revolts began when a fruit vendor set himself on fire in December 2010 to protest police harassment and the lack of economic opportunities — Mr. Panetta will meet with President Moncef Marzouki and Prime Minister Hamadi Jebali, and start talks on American military support in the volatile region. “They have concerns about how to deal with Al Qaeda,” Mr. Panetta said.

He will also visit Jordan and Egypt. Administration officials continue to prod Egypt’s military to hand over authority to a civilian government. The transition has been chaotic, and the Pentagon, which has close ties to Egypt’s generals, has been central in the so-far unsuccessful effort to persuade the military to give up its political powers. “We strongly support an orderly, peaceful, legitimate transition to a democratic system of government,” he said.