The State Department officials on Tuesday declined to describe Myanmar's persecution against Rohingya Muslims as “ethnic cleansing”.
The Senate Foreign Relations Committee, led by Republican Bob Corker, held a hearing on U.S. policy on Myanmar, over the persecution on the Rohingya in Rakhine State.
Although some lawmakers called the violence ethnic cleansing, State Department representatives said the agency could not yet make that declaration.
"I am not in a position to characterize it today. But I do want to say that, to me, this very closely resembles some of the worst kind of atrocities that I've seen over the course of a long career," said Mark Storella, a State Department official.
“This is ethnic cleansing," ranking member Senator Ben Cardin said, citing UN statements. "I think it's genocide. I know there'll be some discussion about it, whether it's genocide or not."
Cardin said the Myanmar military is trying to destroy the population and the U.S. should be outraged about what is happening.
"We need to see the international community come together and say, ‘no, we will not let this continue … that we'll hold those accountable that are responsible,’" he added.
The Rohingya, described by the UN as the world's most persecuted people, have faced heightened fears of attack since dozens were killed in communal violence in 2012.
The UN has documented mass gang rapes, killings -- including infants and young children -- brutal beatings and disappearances committed by security personnel. UN investigators said such violations may have constituted crimes against humanity.
Senator Jeff Merkley criticized President Donald Trump for remaining silent about the violence toward Rohingya.
"This ethnic cleaning, 288 Rakhine villages destroyed and not one word from our president. Thousands of children slaughtered, not one word from President Trump," Merkley said. "Thousands of women raped, thousands of men and women shot as they fled villages, 600,000 refugees, and not one word from our president during this horrific situation."
Since Aug. 25, an estimated 603,000 Rohingya have crossed Myanmar's western state of Rakhine into Bangladesh, according to the UN.
The refugees are fleeing a military operation in which security forces and Buddhist mobs have killed men, women and children, looted homes and torched Rohingya villages. According to Bangladeshi Foreign Minister Abul Hassan Mahmood Ali, around 3,000 Rohingya have been killed in the crackdown.