McKenzie did not speculate on what the review's potential outcome might be, but acknowledged that it is creating concerns in Saudi Arabia.
"I think they want reassurance that they're going to be helped if they're attacked by Iran, and they want help against the continuing attacks," McKenzie, the head of U.S. Central Command, told ABC News and Associated Press reporters traveling with him this week to the Middle East.
McKenzie said Sunday that that while the American military troop presence in the region has deterred Iranian aggression against Saudi Arabia, he believes that what is "far more important is sort of the broad spectrum of capabilities that we give them."
He cited the linking of Saudi and American Patriot missile defense systems that provide an improved early warning system should Iran launch a missile strike at Saudi Arabia.
"The point that I made today and we continue to make it all the time is: It's not actually the types of equipment that are here, it's maximizing the use of the more than 20 Patriot batteries that you do have the interoperable with us, maximizing those capabilities, so that if trouble occurred we can certainly come back in very quickly to help our Saudi friends," McKenzie said.
"I believe our posture in the theater has prevented a state on state attack from Iran," he added.
But he also acknowledged his belief that the U.S. presence in the region has not stopped Iran's proxies from carrying out attacks.
"They're under constant bombardment from Yemen, with a variety of ballistic missiles, cruise missiles and small UAS (unmanned aerial systems) they're very concerned about . We want to help them with that," McKenzie said.
According to McKenzie, in the past three months Iranian-backed Houthi forces in Yemen have fired about 100 ballistic missiles, cruise missiles and drones at Saudi Arabia.
"They're proxies of Iran, so they're under constant bombardment, so they feel that they are under attack, and they are under attack," he said.
U.S. efforts linking Saudi Patriot missile batteries with American batteries surged into Saudi Arabia have helped Saudi Arabian forces intercept a good number of the missiles launched from Yemen.
McKenzie believes it's important to maximize the capabilities of American weapon systems in the region, and he is also aware that a reduction in troop numbers could lead to Iranian provocations.
He believes the reduction of American troop levels in 2019 led to a cycle of Iranian escalatory provocations that culminated in Iran's rocket attack on Al Asad airbase in Iraq last January.
That Iranian attack was triggered by a U.S. airstrike in Baghdad that killed Qassem Soleimani, a top leader of the Islamic Revolutionary Guard Corps' Quds Force.
While it is possible that an American troop reduction in the region could create opportunities for Russia and China to fill the gap with potential weapons sales, McKenzie is not too concerned by that possibility.
"I think we're still going to have a presence here. It might not look exactly like the presence it was five or seven years ago where we get hundreds and thousands of forces here, but I think we're going to play very smart games to leverage what we have," he said.
"And it's not necessarily just a ship or just a submarine or just an aircraft carrier, it's the whole of U.S. government approach," McKenzie said.