U.S. Defense Secretary Leon Panetta said sanctions would add to diplomatic pressure. (Kevin Lamarque/Reuters)

Defense Secretary Leon E. Panetta on Monday called for more time to allow sanctions aimed at Iran to work and disputed statements by top Israeli officials that the sanctions were doing nothing to stop Iran’s nuclear program.

Panetta, who is visiting Tunisia as part of a five-day trip through the Middle East and North Africa, said that although the results of the sanctions “may not be obvious at the moment,” they were hurting Iran’s economy and forcing the country’s leadership to look for a diplomatic solution.

His comments contrasted with those of Israeli Prime Minister Benjamin Netanyahu, who said Sunday that the sanctions and diplomacy “so far have not set back the Iranian program by one iota.”

The U.S. defense secretary is expected to visit Israel on Tuesday, meeting with Netanyahu and Israeli Defense Minister Ehud Barak. His trip is the latest in a series of visits to Israel by high-level Obama administration officials who have sought to express support for the Jewish state while counseling patience with the program of sanctions currently in place.

Panetta, speaking at an American World War II cemetery in Tunisia, called for the international community to remain unified in its support for sanctions against Iran, which are supposed to ratchet tighter in coming weeks and months.

His trip also comes on the heels of a visit to Israel by Republican U.S. presidential candidate Mitt Romney, whose campaign has sought to cast Romney as more supportive of Israel than the Obama administration.

After his meetings with Tunisian officials, Panetta said the government was requesting American help with counterterrorism assistance and training to ensure that a North African offshoot of al-Qaeda, which has made recent gains in Mali, does not make inroads into Tunisia.

Panetta said the United States could offer help with intelligence gathering but did not specify what assistance might be provided.

Panetta made his remarks at a cemetery where 2,481 U.S. troops from World War II are buried and 3,424 missing American service members are memorialized. Accompanied by U.S. Marines, Panetta laid a wreath at the memorial inscribed with the words: “Some there be which have no sepulchre. Their name liveth for evermore.”

As he set down the wreath, bells played the U.S. national anthem. An honor guard of Tunisian soldiers in crisp khaki uniforms stood watch.