The US has purchased Argentine pesos, taking the next step in a controversial effort to calm a currency crisis hitting the South American country and its president, Trump ally Javier Milei.

Treasury Secretary Scott Bessent announced the purchase on social media, while saying the US had finalised terms of a planned $20bn (£15bn) financial rescue for the country.

"The US Treasury is prepared, immediately, to take whatever exceptional measures are warranted," he said.

The announcement helped boost the peso and Argentine debt on financial markets but renewed debate in the US, where the decision to extend financial support to Argentina at a time of spending cuts at home has drawn scrutiny.

"Instead of using our dollars to buy Argentine pesos, Donald Trump should help Americans afford health care," Democratic Senator Elizabeth Warren wrote on social media in response to the announcement, referring to a key issue driving a stand-off over the government shutdown in the US.