By Nicolas Parasie And Jay Solomon 

SHARM EL-SHEIKH, Egypt--Saudi Arabia, Kuwait and the United Arab Emirates pledged $12 billion to help stabilize Egypt's economy, in the latest moves by these Persian Gulf states to rally behind Cairo's general-turned-president, Abdel Fattah Al Sisi.

But the Obama administration didn't provide any new economic or military assistance to Egypt at an international conference on the Red Sea, highlighting the continued concern in Washington about the pace of political reform in the country.

Secretary of State John Kerry announced no new U.S. financial aid for Cairo after holding a bilateral meeting with Mr. Sisi in the resort town of Sharm el-Sheikh.

Washington also continues to hold back providing new military assistance to Egypt, which is facing threats from Islamic extremists both in neighboring Libya and the Sinai Peninsula.

Mr. Kerry led a delegation of U.S. executives attending the investment conference, including representatives from General Electric Co., Microsoft Corp. and Coca-Cola Co.

"The United States is committed to supporting Egypt's economic reforms, and I think that we can already see from what is happening that those are taking hold," Mr. Kerry said, speaking at the tail end of a long list of Arab monarchs and African statesmen.

"We all know also that there are challenges," he added. "And yet every single one of us are here because through those challenges we see and understand the extraordinary potential."

Mr. Sisi's ascension to power last year, in the wake of a military coup d'état he led in 2013, has placed the U.S. at odds with some of its closest Arab allies.

Saudi Arabia and the U.A.E., in particular, have strongly backed Mr. Sisi and his crackdown against the Muslim Brotherhood Islamist movement, which briefly came to power in Cairo in 2011 following the overthrow of long-serving dictator, Hosni Mubarak.

Saudi and Emirati officials on Friday heralded Mr. Sisi as the linchpin for security in the Middle East and a central cog in the fight against Islamic State and al Qaeda.

"We all have to stand by Egypt because its security and stability is the cornerstone in the security and stability of the region," said the prime minister of the U.A.E. and ruler of Dubai, Sheik Mohammed bin Rashid Al Maktoum.

The Obama administration has voiced concerns about the lack of political freedoms in Egypt, and Mr. Sisi's crackdown on the media and non-governmental organizations.

Riyadh and Abu Dhabi have committed more than $20 billion to the Egyptian government since 2013 coup. The Obama administration has pledged less than $2 billion and has placed a hold on some military equipment, including F-16 fighter jets.

Saudi Arabia's Crown Prince Muqrin bin Abdulaziz appeared to take a swipe at the Obama administration, charging some foreign governments were judging Cairo and its fight against extremism differently from their own campaign.

"We underline our firm stand behind the people and government of Egypt," the Saudi royal said. "We call on the international community not to follow double standards."

Egypt's economy has been struggling since political turmoil erupted in 2011 but the largesse of the Persian Gulf states and a more recent economic turnaround plan have markedly improved growth prospects.

Mr. Sisi acknowledged the support from the Persian Gulf and opened an economic conference in Sharm-El-Sheikh by thanking Saudi Arabia, the United Arab Emirates and Kuwait.

The Egyptian president vowed to reduce unemployment and combat terrorism as he attempts to jump-start his country's economy.

Egypt's economic revival also hinges on maintaining domestic security. In the past few months, there has been a rise in violence as a result of Mr. Sisi's government battle with Islamists.

The North African country is working on "a model for an Arab and Islamic civilization with its true tolerant values. A country that renounces violence, terrorism and extremism," Mr Sisi said. In Sharm-El-Sheikh, where Mr. Sisi made his speech, security forces were deployed widely, with helicopters circling the resort.

Economists have said that one of Mr. Sisi's biggest challenges is tackling unemployment. Egypt, the Arab world's most populous country with about 90 million people, experiences widespread youth unemployment, considered one of the main reasons behind the mass protests that led to the downfall of Mr. Mubarak.

Mr. Sisi said two-thirds of Egypt's population is under the age of 40, and 30 million people are at employment age.

Write to Nicolas Parasie at nicolas.parasie@wsj.com and Summer Said at summer.said@wsj.com