Democrats have demanded records from the president's personal lawyer, the next step of an effort that could remove Donald Trump from office.
Rudy Giuliani has admitted to asking Ukrainian officials to investigate widely debunked corruption allegations against Democratic rival Joe Biden.
Lawmakers issued a subpoena for those communication records from Mr Giuliani.
The request is part of impeachment proceedings against Mr Trump, spurred by a whistleblower complaint.
The whistleblower, reportedly a CIA officer, revealed concerns among a number of White House officials that Mr Trump had attempted to pressure a foreign leader into investigating a Democratic political rival.
A rough transcript emerged last week of that call between Mr Trump and President Volodymyr Zelensky, revealing that Mr Trump urged Mr Zelensky to investigate the discredited allegations against Mr Biden, a 2020 Democratic frontrunner, and his son.
On Monday it emerged that the US secretary of state, Mike Pompeo, had listened in on the call, which is now at the centre of an impeachment inquiry against the president. Mr Pompeo was last week served with a subpoena by House Democrats.
And in a separate development on Monday, it emerged that President Trump had pushed another foreign leader for help connected to his domestic political situation. The Australian government confirmed that Mr Trump asked Prime Minister Scott Morrison to help assist the US attorney general, Bill Barr, with an investigation into the Russia inquiry that dogged Mr Trump's first two years in office.
The White House reportedly restricted access to the call's transcript to a small group of the president's aides – as officials had done with the transcript of the controversial Ukraine call.
Why was Giuliani served with a subpoena?
Three chairmen of key House of Representatives committees – Intelligence, Foreign Affairs and Oversight – sent the subpoena notice to Mr Giuliani on Monday.
The subpoena was expected, as Democrats had earlier said they wanted to question Mr Giuliani, a central figure in the saga.
On the phone call, Mr Trump asked the Ukrainian president to co-ordinate with his lawyer on any inquiry into Mr Biden and son Hunter.
During a 19 September appearance on CNN, Mr Giuliani confirmed he asked Ukraine to "look into the allegations that related to my client, which tangentially involved Joe Biden in a massive bribery scheme".
In their subpoena letter, the chairmen said: "In addition to this stark admission, you stated more recently that you are in possession of evidence – in the form of text messages, phone records, and other communications – indicating that you were not acting alone and that other Trump Administration officials may have been involved in this scheme."
The chairmen have demanded all relevant communications be submitted by 15 October.
Mr Giuliani and the White House have not yet responded to the subpoena, though on Sunday, Mr Giuliani told ABC News he "wouldn't co-operate" with Mr Schiff.
- One feared dead, several others injured after accident at Legon underpass
- Citi FM journalist, Caleb Kudah allegedly picked up by National Security operatives
- We will not allow any religious group to plunge Ghana into chaos – Muntaka
- Kwabena Agyepong welcomed back to NPP after 6 years suspension
- Leadership crisis at Ghana Rugby: Chairman Herbert Mensah suspended indefinitely, set to be removed from office on June 8
- Former British High Commissioner to Ghana, Craig Murray jailed for contempt in the UK
- SALL kicks against EC’s decision to amend C.I. for them to vote in 2024
- Ghana drops to 95th in 2021 World Happiness ranking
- Dr Mavis Owureku Asare: Wesley Girls’ no fast policy is not about religion
- NSMQ 2021: Tamasco and 3 others secure tickets to Accra on day one of Northern Regional qualifiers
UEW Signs MoU with T-TEL to reform Educational Sector
Central Regional House of Chiefs vow to be more development-oriented
New Kejetia Market closed down after Tuesday’s fire
Message from the Morning Man: Albert and the Bees
Asantehene to open Regional Consultative Dialogue on Small-Scale Mining on May 12
Taskforce will curb illegal chainsaw operations – Municipal Director says
Some 155 million people suffer from hunger in 2020 – UN
Students graduate without acquiring the requisite skills needed for the job market – Skills Development expert
Use campaign billboards to educate Ghanaians on road safety – Chiefs urge
GAF are engaged in the decommissioning and demobilizing of equipment used for illegal mining – Abu Jinapor
Kumasi Mayor commends Fire Service for swift response to New Kejetia Market fire
Francis Addai-Nimoh: #FixTheCountry – Drawing the lines of responsibilities
No regional and district Eidul Fitr prayers, security agents to ensure compliance
Unemployed man jailed 11 years for stealing
Azamati’s development as top athlete is fastest in my 11 years – West Texas track coach