US Secretary of State Mike Pompeo has been subpoenaed.
A Democratic-led US House of Representatives committee issued the order on Friday.
They want to him to hand over documents regarding contact the US government had with the Ukrainian government.
Earlier this week House Speaker Nancy Pelosi launched a congressional impeachment inquiry of US President Donald Trump.
Trump not satisfied with Iran's latest proposal, will not 'leave war early'
US President Donald Trump said on Friday he was not satisfied with the latest Iranian proposal for talks on the war, while Iran's foreign minister said Tehran was ready for diplomacy if the United States changes its approach.
Iran sends proposal for negotiations with US to mediator Pakistan
Tehran has submitted its latest proposal for negotiations with the United States, Iranian state media and a Pakistani official said on Friday, a move that could offer hope for breaking a deadlock in efforts to end the Iran war.
Iran threatens painful response if US renews attacks
Iran said on Thursday it would respond with "long and painful strikes" on US positions if Washington renewed attacks and restated its claim to the Strait of Hormuz, complicating US plans for a coalition to reopen the waterway.
US Navy acting 'like pirates' to carry out naval blockade of Iranian ports, says Trump
President Donald Trump said on Friday the US Navy was acting "like pirates" in carrying out Washington's naval blockade of Iranian ports during the US and Israel's war against Iran.
The UAE has welcomed a new resolution adopted by the International Maritime Organization’s (IMO) Marine Environment Protection Committee during its 84th session.
At the United Nations Security Council, the UAE has called for the immediate and unconditional reopening of the Strait of Hormuz, urging that Iran be held fully accountable for obstructing international navigation.
Sheikh Abdullah bin Zayed Al Nahyan, Deputy Prime Minister and Minister of Foreign Affairs, reaffirmed the United Arab Emirates' full support for the sovereign measures taken by Bahrain to safeguard its security, uphold its sovereignty and national achievements, and counter any attempts to undermine its stability.
