U.S. Defense Secretary Leon Panetta arrived in Cairo on Tuesday, July 31 to meet Egypt's new Islamist president and its top general, seeking to balance security concerns with efforts to promote the country's still wobbly transition to democracy, Reuters said.

It will be Panetta's first opportunity to speak with President Mohamed Mursi of the long-banned Muslim Brotherhood.

Political uncertainty is casting a shadow over Egypt's future as the military and the Muslim Brotherhood engage in a power struggle over the future of a country that remains without a permanent constitution, parliament or government.

Panetta told reporters at the start of his week-long trip to North Africa and the Middle East that he would urge Egypt's government "to provide for as broad a coalition as possible within the government".

Mursi, the country's first freely elected leader, has pledged to work for all Egyptians but critics point to a month-long delay in forming a government as early evidence that the leader is unwilling to espouse the kind of compromise that would bring political opponents into his cabinet.

Panetta also wants to bolster the U.S. commitment to a strong military relationship with Egypt in talks with Field Marshal Hussein Tantawi, head of the military council that took over when Hosni Mubarak was ousted and that is vying for influence with Mursi.

Israel - Panetta's next stop on his trip - is particularly worried about the rise of Islamists in place of ousted Arab autocrats, especially Mubarak, who guaranteed his country's 1979 treaty with Israel, the first between Israel and an Arab country.

During a visit by U.S. Secretary of State Hillary Clinton to Egypt in mid-July, Mursi issued assurances that Egypt would abide by its treaties.

The Obama administration publicly backed the revolution that toppled longtime leader Mubarak last year but also sees the Egyptian army as a crucial regional security partner.

The country is also of strategic importance to the United States because of the Suez Canal, a vital conduit for trade and for U.S. military vessels.

Washington released $1.3 billion in military aid for Egypt in March despite misgivings over progress towards democracy, saying U.S. national security required continued military assistance.

Panetta's visit will underscore the somewhat delicate position the United States faces in Egypt. For three decades it strongly supported Mubarak, who repressed and marginalized Mursi's allies in the Muslim Brotherhood.

Since Mubarak's overthrow last year, the Brotherhood has propelled itself to the heart of politics, forcing Washington to put aside its concerns and strengthen its links with the movement.

The Brotherhood has a history of hostile rhetoric towards Israel and its conservative social agenda sits uneasily with U.S. attempts to promote personal freedoms including the rights of women and religious minorities in the Middle East.

Clinton warned on Monday that religious freedom in Egypt appeared to be "quite tenuous", saying the outgoing interim, army-backed government has failed to aggressively prosecute perpetrators of sectarian violence.