Cairo: US Secretary of State John Kerry arrived in Egypt Sunday on a surprise trip to push for democracy in the politically tumultuous country as Washington quietly released $572 million (Dh2.1 billion) in military aid.

Kerry, the highest-ranking US official to visit since President Abdul Fattah Al Sissi came to power, was to press the former army chief during his lightning trip to install greater political freedoms and discuss security challenges.

The top US diplomat’s tour is also focused on trying to find a political solution in Iraq, where Islamic militants were Sunday making new gains in an offensive that has triggered international alarm.

“Obviously this is a critical moment of transition in Egypt, enormous challenges,” Kerry said as he met first with new Foreign Minister Sameh Shoukri. But he vowed “the US is very interested in working closely” with the new government “in order to make this transition as rapidly and smoothly as possible”. Since Islamist president Mohammad Mursi was removed from power, Egypt has been fighting a battle against the Muslim Brotherhood.

US officials warned Washington has deep concerns about the government’s “polarising tactics” and acknowledged they were “balancing” different strategic interests in what is a “complicated” relationship.

Kerry’s visit comes a day after an Egyptian court confirmed death sentences for 183 Islamists, including Muslim Brotherhood chief Mohammad Badie, after a speedy mass trial that sparked an international outcry.

Kerry’s latest diplomatic mission, that will also see him visit Amman, Brussels and Paris, is expected to focus on uniting Iraq’s fractious leaders and urging its neighbours to use their sway to ensure the speedy formation of a new government while cutting the flow of funds to the militants.

US officials also revealed that $572 million in aid, which had been frozen since October, was released to the Cairo government about 10 days ago after finally winning a green light from Congress. It will mainly go to pay existing defence contracts.

US officials announced in April they planned to resume some of the annual $1.5 billion in mostly military aid to Cairo, including 10 Apache helicopter gunships for counterterrorism efforts in the Sinai Peninsula.

But the aircraft remain in storage in the US, an official confirmed Sunday.

Al Sissi won some 97 per cent of the vote in May elections nearly a year after the toppling of Morsi, and installed an interim government.

“There’s a strong desire on the part of the United States for this transition to succeed,” a senior State Department official told reporters travelling with Kerry.

“We have a long-standing relationship ... that’s built on several different pillars. It’s at a difficult juncture right now, that’s true, and we have serious concerns about the political environment,” the official said.

Egypt, one of only two Arab nations to have a peace treaty with Israel, has long been seen as a key strategic ally and a cornerstone to regional stability.

But the political turmoil since the 2011 uprising that toppled strongman Hosni Mubarak has paralysed Egypt, leaving it more concerned with domestic problems than regional matters despite the upheavals of the Arab Spring.

Shoukri hoped for “a fruitful discussion” saying Kerry’s trip was “a very important visit for us and for our bilateral relations, and also given the regional situation.”

Washington’s concerns about Cairo include a new law controlling demonstrations, “the lack of space for dissent, mass trials and death sentences”, the official said.

“We are concerned that some of the tactics they’re using to address their security issues are polarising ... they in some ways radicalise certain aspects of Egyptian society in ways that are not supportive of overall stability.”

Kerry was also hearing directly from civil society leaders about the situation in the country in a round-table at a Cairo hotel.

Kerry will insist in his meetings that the United States still needs to see a return to the rule of law if US-Egypt ties are to improve.