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 says operation to reopen Strait of Hormuz will be 'paused'
US President Donald Trump has announced on Tuesday that he would briefly pause the operation to escort ships through the Strait of Hormuz, dubbed "Project Freedom", citing "great progress" towards an agreement with Iran, while the blockade remains in force.
Hantavirus-hit cruise ship to head to Spain after being granted permission
A luxury cruise ship that has been hit by an outbreak of the deadly hantavirus was preparing to travel from Cape Verde towards Europe on Wednesday after the Spanish government gave permission for it to dock in the Canary Islands.
Russian attacks kill 27 before deadline for ceasefire proposed by Kyiv
Russian attacks throughout eastern Ukraine have killed at least 27 people on Tuesday, including 12 in one of the worst strikes so far this year, hours before a midnight deadline ushering in an open-ended ceasefire proposed by Kyiv.
Eight dead in fire at shopping centre west of Tehran, Iranian media say
At least eight people died and 36 were hurt after a fire broke out in a shopping centre west of Tehran on Tuesday, Iranian state broadcaster IRIB reported.
Trump says Iran should wave the white flag of surrender
US President Donald Trump on Tuesday dismissed Iran's military capability and said Tehran "should wave the white flag of surrender" but is too proud to do so.
