US Secretary of State Mike Pompeo has been ordered by Democrats to turn over documents relating to the Trump administration’s dealings with Ukraine.
In a letter, the heads of three House committees subpoenaed Mr. Mike Pompeo to produce the documents within a week.
It is the latest move in rapidly escalating impeachment proceedings against President Donald Trump.
He is being scrutinised for pushing Ukraine’s president to investigate his Democratic rival, Joe Biden.
In a separate development on Friday, the US special envoy for Ukraine negotiations, Kurt Volker, resigned, according to US media reports.
Washington has been rocked by a complaint from an intelligence whistleblower that Mr Trump was “using the power of his office to solicit interference from a foreign country in the 2020 US election”.
Mr Trump had denied putting any pressure on Ukrainian President Volodymyr Zelensky in a phone call in July when Mr Biden was leading polls to win the Democratic nomination for the White House race.
But a transcript of the call released by the White House showed that the president did press Mr Zelensky to investigate Mr Biden.
Mr Trump has alleged that Mr Biden pressed for the sacking of Ukrainian prosecutor Viktor Shokin in 2016 to protect a business that employed his son, Hunter Biden.
Mr Biden did call for the sacking of Mr Shokin, even threatening to withhold $1bn (£813m) in aid to Ukraine. But so did a number of other Western officials who saw Mr Shokin as a hindrance to anti-corruption investigations.
Impeachment is a rarely exercised two-stage political process by which a US president can be removed from office for wrongdoing.
Even if the House of Representatives impeached President Trump, he is unlikely to be forced out of the White House because Republicans control the Senate.
The US president has dismissed the impeachment proceedings as a “hoax” and “another witch-hunt”.
What is the Pompeo subpoena about?
The subpoena was issued in a joint letter by the House’s Foreign Affairs, Intelligence and Oversight committees.
The committees are headed by Elliot Engel, Adam Schiff and Elijah Cummings, respectively.
In the letter, the committees said they were investigating “the extent to which President Trump jeopardized national security by pressing Ukraine to interfere with our 2020 election and by withholding security assistance provided by Congress to help Ukraine counter Russian aggression”.
They added that the subpoena was issued because Mr Mike Pompeo had failed to comply with demands to provide relevant documents.
They said his refusal “impairs Congress’ ability to fulfil its constitutional responsibilities to protect our national security and the integrity of our democracy”.
The three committees also scheduled testimony from five other State Department officials – including Mr Volker and the former US ambassador to Ukraine, Marie Yovanovitch.
Mr Mike Pompeo is yet to publicly comment on the subpoena.