LOS ANGELES (BLOOMBERG) - About 13 million people watched the first day of public testimony in the House impeachment investigation of United States President Donald Trump across the major broadcast and cable TV channels.

Fox Corp's Fox News drew the highest total audience with 2.9 million viewers, followed closely by Comcast Corp's MSNBC with 2.7 million.

The total-viewership figure roughly compares with the 19.5 million viewers who watched former Federal Bureau of Investigation director James Comey's congressional testimony in June 2017.

Wednesday's hearing featured two experienced diplomats detailing their concerns that the President tried to leverage his office for personal political gain, including a new account of Mr Trump stressing his desire for Ukraine to investigate a rival.

While Democrats had released transcripts of their previous testimony as part of their impeachment inquiry, the lawmakers had hoped that having the witnesses speak in front of a large televised audience would help build more public support for their case.