A spokeswoman for the US State Department, Katina Adams, said the United States was aware of reports of the general's replacement.
Suu Kyi has seen her reputation tarnished as the violence continues.
The official said Suu Kyi has been "very forthcoming" about wanting to solve the problem and wields a lot of influence.
In its most forceful denial so far, however, Myanmar's military issued a statement late Monday saying security forces did not commit atrocities during "clearance operations".
The official did not comment on whether Tillerson would raise the threat of military sanctions, which USA lawmakers have pushed for.
The U.N. humanitarian office said Tuesday that the number of Rohingya who have fled Myanmar to Bangladesh since August 25 has risen to 618,000.
However, Tillerson said more information was needed for Washington to use that language, and called for an independent inquiry into the causes of the crisis and alleged atrocities.
Suu Kyi has assured other Southeast Asian nations that her government is implementing the recommendations of a commission led by Annan on the situation in Rakhine state, where more than half a million Rohingya Muslims have fled to neighboring Bangladesh.
The crisis erupted after Rohingya rebels attacked police posts in Myanmar's Rakhine state, triggering a military crackdown that saw hundreds of villages reduced to ashes and sparked a massive exodus.
In a highly publicized September speech on the situation in Rakhine, Suu Kyi said Myanmar was not "afraid of global scrutiny", but did not denounce alleged atrocities against the Rohingya community and appeared to ignore the findings of a report commissioned by her administration.
Serena Williams getting married in New Orleans Thursday
The tennis champion, 36, is saying "I do" to the Reddit co-founder, 34, in an intimate ceremony in New Orleans, Louisiana. The couple are said to be bringing a nanny along to the wedding to take care of their baby.
"This is a tremendous concern to Canada and to many, many countries around the world", Trudeau told a news conference in Manila.
The stream of desperate refugees who escape across the riverine border bring with them stories of rape, murder and the torching of villages by soldiers and Buddhist mobs.
On Friday, the Burmese military replaced the commanding officer in Rakhine State.
During his visit to the Myanmar capital Naypyidaw, his first to the country, Tillerson pledged an additional $47 million in aid for refugees, bringing the total the U.S. has earmarked for the crisis to $87 million since August.
Suu Kyi, a former democracy activist, has been lambasted by rights groups for failing to speak up for the Rohingya or condemn festering anti-Muslim sentiment in the country.
Human rights groups poured scorn on Tuesday on a Tatmadaw investigation into alleged atrocities against Rohingya Muslims, branding it a "whitewash" and calling for United Nations and independent investigators to be allowed into Burma.
He said he impressed on Duterte the need for respect for the rule of law and offered Canada's support and help.
"I can not hide my deep concern with the dramatic movement of hundreds of thousands of refugees from Myanmar to Bangladesh", Guterres told leaders including Suu Kyi.
He described the situation as a potential source of instability in the region, as well as radicalisation.