U.S. Defense Secretary Lloyd Austin travelled to Egypt on Wednesday to tell Cairo it wanted to deepen security and other ties but was concerned about human rights in country where activists say government critics are regularly rounded up.

Egyptian President Abdel Fattah al-Sisi, who as army chief led the 2013 ouster of Egypt's first democratically elected president, has cracked down on political dissent, including liberal critics and Islamist opponents.

Rights groups say tens of thousands of people have been detained, with many held in pre-trial detention for long periods.

"I fully expect him to bring up human rights, respect for fundamental freedoms," said a senior U.S. defense official, speaking on the condition of anonymity.

Sisi says Egypt's security is paramount and the government promotes human rights by providing basic needs such as jobs and housing.

The United States has long provided Egypt with large amounts of military and other aid, ever since the Arab world's most populous nation signed a peace deal with neighbouring Israel in 1979. Cairo has remained a close regional ally of Washington.

But Washington has withheld small amounts of military aid to Cairo, citing a failure to meet human rights conditions, and advocacy groups have pushed for more to be held back.

"Egypt shouldn't get a blank check from the United States when it continues to violate basic human rights, and I hope Secretary Austin will use this opportunity to convey that message to President Sisi," U.S. Democratic Senator Chris Murphy told Reuters.

U.S. President Joe Biden has pledged to put human rights at the heart of his foreign policy and rights advocates have pushed Washington to get tougher on Sisi.

But some current and former U.S. officials say the United States can only take limited steps against Egypt and other allies on rights issues if it wants to avoid rival powers gaining influence.

"They would simply, probably out of necessity, move toward Russia or China or whoever else they considered to be a substitute for the United States and then their interest in trying to adhere to international human rights standards would be less," said Michael Mulroy, a former Pentagon official.