US Democratic lawmakers have demanded documents from the White House as part of their impeachment inquiry into President Donald Trump.
The documents relate to a call between Mr Trump and Ukrainian President Volodymyr Zelensky on 25 July.
In the call, Mr Trump pushed Mr Zelensky to investigate his leading Democratic political rival, Joe Biden.
The impeachment inquiry stems from the call, which was flagged up by a whistleblower in August.
Mr Trump has denied any wrongdoing, accusing his political opponents of a “witch hunt”.
But in a move to crank up the pressure on the president, the three House committees leading the investigation have given him until 18 October to hand over the documents.
“We deeply regret that President Trump has put us – and the nation – in this position, but his actions have left us with no choice but to issue this subpoena,” the Democrats wrote in a letter to the White House.
he subpoena – an order to hand-over evidence – was issued on Friday by the chairmen of the committees for Oversight, Intelligence and Foreign Affairs.
White House press secretary Stephanie Grisham sought to play down the subpoena, saying it “changes nothing”.
A separate request for records has also been sent to Vice-President Mike Pence, with Democrats asking him to clarify “any role you may have played” in Mr Trump’s overtures to Ukraine.