The United States has delivered 10 Apache helicopters to Egypt in recent weeks after lifting part of a freeze on aid to the north African nation, a US official said Saturday.

US Secretary of State John Kerry had been promising Cairo's new leadership that the aircraft -- aimed to join counter-terrorism operations in the Sinai peninsula -- would be delivered soon.

"They got there a few weeks ago," a US senior administration official told AFP.

Kerry announced in June that he was "confident" Egypt would receive the helicopter gunships soon, and reiterated that in a phone call to Foreign Minister Sameh Shoukry.

The United States annually allocates some $1.5 billion in aid to Egypt, including $1.3 billion in military assistance.

That was frozen in October 2013 on condition that democratic reforms be enacted after the July 2013 military-led overthrow of Islamist elected president Mohamed Morsi and a vicious crackdown on his followers.

Washington said in April it planned to resume some of the annual aid for counterterrorism efforts in the Sinai Peninsula.

US President Barack Obama spoke to his Egyptian counterpart Abdel Fattah al-Sisi on Thursday and expressed concern over mass trials and the continued detention of journalists and peaceful activists.

During a telephone call, the White House said, Obama encouraged Sisi to "invest in the political, economic, and social aspirations of the Egyptian people."

"President Obama also expressed concern about mass trials, the status of NGOs, and the continued imprisonment of journalists and peaceful activists in Egypt," the statement said.

Egypt's military has been battling an insurgency on the peninsula since it overthrew Islamist president Mohamed Morsi last year and cracked down on his supporters.

The government declared a state of emergency in parts of North Sinai after an October 24 suicide attack near El-Arish killed 30 soldiers in the deadliest assault on security forces since Morsi's ouster.

Militant groups claim their attacks are in retaliation for a government crackdown targeting Morsi's supporters that has left hundreds dead and thousands jailed.