Vice President-elect Mike Pence has said he hopes Congressman John Lewis "reconsiders" his belief that Donald Trump will not be a legitimate president and decides to attend his inauguration.
Mr Lewis, a veteran of the civil rights movement who was beaten by police during the famous march in Selma, Alabama, said "it's going to be hard" to work with Mr Trump and that the alleged actions of the Russian government during the election invalidated the incoming administration.
The Georgia Democrat provoked a Twitter storm from Mr Trump, who said he "should spend more time on fixing and helping his district, which is in horrible shape and falling apart".
Mr Pence, the Indiana governor, told Fox News Sunday: "While I have great respect for John Lewis and for his contributions, particularly to the civil rights movement, I was deeply disappointed to see someone of his stature question the legitimacy of Donald Trump's election as president and say he's not attending the inauguration.
On Saturday Mr Trump accused Mr Lewis of being "all talk, talk, talk - no action or results".
He later added: "Congressman John Lewis should finally focus on the burning and crime infested inner-cities of the US. I can use all the help I can get!"
Others who plan to skip the 20 January inauguration ceremony include Reps Luis Gutiérrez of Illinois, Jared Huffman and Barbara Lee of California, Katherine Clark of Massachusetts, and Raúl Grijalva of Arizona.
Join our new commenting forum
Join thought-provoking conversations, follow other Independent readers and see their replies