Tillerson will meet with the foreign ministers of Saudi Arabia, Egypt, the United Arab Emirates and Bahrain in Jeddah in an attempt to mend fences between the crucial US allies.
But in a setback to his efforts, the four Arab states - which accuse Doha of supporting extremism - yesterday quickly dismissed a counter-terrorism deal signed between Qatar and the United States as "insufficient".
The crisis has presented Tillerson, well known in the Gulf from his former role as chief of energy giant ExxonMobil, with his first big challenge as Washington's top diplomat.
While President Donald Trump welcomed the Arab states' air and land blockade of their gas-rich neighbour, the US State Department has taken a more neutral position and Tillerson is seeking to broker a diplomatic solution.
Tillerson, who is spending much of this week in the Gulf seeking to end the dispute, had an audience with Saudi King Salman at the royal court today after arriving in Jeddah.
He passed on "greetings from President Trump".
"He wanted to ensure that I extend to you his warmest regards," Tillerson told the Saudi ruler.