US defence secretary meets with Egyptian officials in Cairo
According to a Department of Defence statement, Mattis' visit was part of a five-day trip "to re-affirm the enduring US commitment to partnership in the Middle East, West Africa and South Asia."
Mattis was scheduled to meet with Egyptian President Abdel Fattah al-Sisi and Defence Minister Sedki Sobhi.
Mattis later departed for Jordan, where he was scheduled to attend a meeting on countering violent extremism in West Africa, hosted by Jordan's King Abdullah II.
On Monday, Mattis will be visiting Pakistan with plans to meet with Prime Minister Shahid Khaqan Abbasi before concluding his trip with a visit to Kuwait the following day.
Egypt is among the top recipients of US military assistance, receiving nearly $1.3 billion annually in addition to $250 million in economic aid.
That assistance is linked to Egypt's 1979 peace treaty with Israel, and underpins a US-Egyptian security relationship that is now mostly aimed at fighting terrorism.
Following the Sinai attack which killed more than 300 people, Sisi instructed his security forces to use "all brute force" and gave them three months to restore stability in the volatile northern part of the Sinai Peninsula.
Northern Sinai has been the epicentre of an Islamic insurgency for years; the insurgency intensified following the 2013 ouster of Sisi's predecessor, ousted president Mohammed Morsi.
Egypt's security forces have been waging a tough and costly campaign against militants in the area, where the local IS affiliate spearheads the insurgency.
But Sisi's government has also expanded military ties with Russia and signed deals to buy Russian fighter jets, helicopters and other weapons.
Russian Defence Minister Sergei Shoigu visited Cairo on Wednesday, noting that military cooperation between the two countries has increased recently as Egypt placed new orders for Russian weapons.
In a move that could further irk the Americans, Russia approved a draft agreement with Egypt for Russian warplanes to use Egyptian military bases, according to a document released on Thursday — a deal that would allow Moscow to further increase its military footprint in the Mideast.