Trump attempts to discredit whistle-blower in impeachment probe

US president denounces impeachment investigation against him as a ‘coup’ as more witnesses are called to testify.

US President Donald Trump has denounced an impeachment investigation against him as a “coup”.

A war of words between House Democrats and a key member of his cabinet has erupted in Washington, DC, as more witnesses are being called to testify in an impeachment inquiry.

Al Jazeera’s Heidi Zhou-Castro reports from Washington, DC.