WASHINGTON (Reuters) - The U.S. House of Representatives Oversight Committee has invited President Joe Biden's son Hunter to testify on March 20 as part of the panel's impeachment investigation of the president, the panel said in a statement on Wednesday.

Republican investigators have focused on Hunter Biden's work for businesses in Ukraine and China while his father served as U.S. vice president from 2009 to 2017. So far they have turned up no evidence of wrongdoing by the elder Biden, even as they have highlighted his son's struggles with substance abuse.

(Reporting by Jasper Ward; writing by Paul Grant; editing by Eric Beech)