The United Nations special rapporteur on human rights in Myanmar, Yanghee Lee, said a full purge could be the ultimate goal of the institutional persecution and horrific violence being perpetrated against the Rohingya.
The evidence "indicates the government may be trying to expel the Rohingya population from the country altogether," Lee told the UN rights council.
The army launched a bloody crackdown against the Rohingya in October in the northern Rakhine state following attacks by militants on several border posts.
UN investigators say that during the military operation women were gang-raped by soldiers and Rohingya babies were slaughtered.
Lee wants the rights council to establish the UN's highest-level probe, a Commission of Inquiry (COI), to investigate that crackdown as well as violent episodes in 2012 and 2014.
The council could set up the commission before its session ends later this month, but key players including the European Union have not yet backed Lee's call because of concern that a damning UN investigation might threaten the country's fragile democracy drive.
Speaking to reporters after her council appearance, Lee said she believed support for a Commission of Inquiry was tepid, including within the EU.
Countries "won't say they are not going to support your call, but I do hear ... (countries) say that maybe Aung San Suu Kyi needs more time," Lee said, referring to the Nobel peace laureate who leads Myanmar's civilian government.
Suu Kyi's government, which took charge last year after decades of oppressive military rule, has rejected Lee's bid to set up a Commission of Inquiry and insisted its own national probe can uncover the facts in Rakhine.
Lee conceded to reporters that a full international probe "could have a destabilising affect" in that it may implicate the military in crimes against humanity, but she insisted it was in the government's interest to get the facts out.
She also told the council that the government's internal probe had already been proved inadequate.
Representatives from the EU, The Netherlands and Britain all avoided the question of a Commission of Inquiry during Monday's discussion.
Britain's envoy to the council, Julian Braithwaite, said the international community needed to "engage (Myanmar) without damaging the delicate civilian/military balance".