The 80-year-old monarch is on a rare five-day visit to Egypt, a trip seen as a clear show of support for Egyptian President Abdel Fattah al-Sisi, the former military chief who toppled his Islamist predecessor Mohamed Morsi in 2013.
The two leaders have already signed a slew of multi-billion-dollar investment deals, and yesterday Egypt agreed to demarcate its maritime borders with Saudi Arabia by officially placing two islands in the Straits of Tiran in Saudi territory.
In December, Saudi Arabia announced the creation of an "anti-terrorism" coalition whose members it said would share intelligence, counter violent ideology and deploy troops if necessary to combat extremists.
The kingdom is part of the US-led coalition bombing the jihadist Islamic State group in Iraq and Syria.
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Riyadh is also leading an Arab coalition, of which Egypt is a member, that has been bombing Iran-backed Huthi Shiite rebels in Yemen.
It has since pumped billions of dollars in aid and investment into Egypt.
Yesterday, King Salman and Sisi agreed to set up a USD 16 billion investment fund, and also settled the long-standing maritime dispute.
Salman announced on Friday a plan to build a bridge over the Red Sea to Egypt, and inked several other agreements Egypt hopes will boost its battered economy.
His visit follows months of reports in Saudi and Egyptian newspapers of strained ties over Cairo's unwillingness to participate fully in operations against Huthi rebels in Yemen.
For Saudi Arabia, which is in competition with regional rival Iran, keeping Egypt under its aegis is crucial, and it has played a key role in propping up Egypt's economy.