Migrant arrivals to the US for the 2022 fiscal year topped two million for the first time in the country's history.
Newly released government data shows a significant increase in people coming from Venezuela, Nicaragua and Cuba.
The number of unique migrants increased slightly in August at 2.2 per cent compared to July, figures from a US Customs and Border Patrol report show.
Of the 157,921 people encountered last month, 55,333 were from Venezuela, Nicaragua or Cuba — representing a 175 per cent increase from this time last year.
US authorities encountered 56,979 migrants from Mexico and northern Central American countries, a 43 per cent decrease compared to August 2021.
Border authorities stopped migrants 203,598 times in August, a slight increase from July but down from the 209,840 encounters in August of last year.
Migrants were stopped by US authorities 2.1 million times during the fiscal year beginning on October 1, the first time the figure exceeded two million.
The Customs and Border Patrol report said that more people stopped at the border will be “removed or expelled” this year than in any other.
Under Title 42, migrants who seek asylum in the US are sent to Mexico while they await their immigration court date. Mexico accepts migrants expelled under the pandemic-era policy if they are from Guatemala, Honduras or El Salvador.
Migrants from Venezuela, Nicaragua and Cuba are difficult to expel because of America's strained ties with the three countries.
“Failing … regimes in Venezuela, Nicaragua and Cuba are driving a new wave of migration across the Western Hemisphere, including the recent increase in encounters at the south-west US border,” Customs and Border Patrol Commissioner Chris Magnus said in Monday's report.
“Those fleeing repressive regimes pose significant challenges for processing and removal.”
White House Press Secretary Karine Jean-Pierre told reporters on Tuesday that the White House is working to process asylum seekers in a “safely, orderly and humane way”.
US President Joe Biden's border policy remains a target of Republican criticism, reflected in moves from conservative border-state governors to transport migrants to northern liberal-leaning cities.
Florida Governor Ron DeSantis last week flew about 50 Venezuelan migrants to the island of Martha's Vineyard in Massachusetts. A day later, Texas Governor Greg Abbott transported busloads of Venezuelans, Nicaraguans and Cubans to Washington, where they were dropped off outside Vice President Kamala Harris's home.
Ms Jean-Pierre said the Biden administration is co-ordinating with state and local officials to accommodate the migrants as they await their asylum claims.
Texas has transported more than 11,000 immigrants to Washington, New York and Chicago, Mr Abbott's office said.
Mr DeSantis was expected to send another plane of migrants to Mr Biden's home state of Delaware on Tuesday afternoon, US media reported.
Ms Jean-Pierre called the reported decision a "political stunt" and added that migrants are fleeing persecution in their countries “only to be used as a political pawn”.