The Pentagon chief made the comments on Thursday after talks in Cairo with Egyptian President Abdel Fattah el-Sisi.
“I left Cairo very confident, very confident in the avenues we have to advance our military-to-military relationship, which has been a bedrock and has stood solid all these years,” Mattis told reporters in Tel Aviv, without elaborating.
Mattis is the first cabinet level official in the administration of President Donald Trump to visit Egypt.
A Pentagon official said Mattis’ meetings with Sisi and Egypt’s defense minister had focused on rebuilding trust and stronger military ties.
Relations between Washington and Cairo have started to warm under Trump. Earlier this month, Trump moved to reset US relations with Egypt, hosting Sisi for talks at the White House and giving him firm backing.
The Trump administration has signaled that Egypt will continue to receive its $1.3 billion worth of annual military aid. Obama froze aid to Egypt for two years after Sisi, then a general, overthrew President Mohamed Morsi in mid-2013.
Obama’s ban soured relations between the two countries and prompted Egypt to purchase weapons from Russia and France.
Alarmed by Cairo’s tilt towards Moscow, Washington resumed the annual military assistance. Obama justified the move as being “in the interest of US national security.”