White House tells Pelosi Trump won't participate in impeachment inquiry, claiming it's unconstitutional; Sources: Trump aides alerted national security lawyers about his Ukraine call, raising concerns and seeking to contain damage;

From The Situation Room with Wolf Blitzer and Pamela Brown CNN Podcasts

House Democrats to subpoena key witness in Ukraine scandal investigation after White House blocked his testimony; Poll: majority of Americans support launch of impeachment inquiry, including nearly three-in-ten republicans; Former Representative Trey Gowdy joins Trump legal team; Syrian war defector calls on Congress to take action after revealing atrocities committed by Assad regime; Parents of British teen killed in car crash ask Trump to return U.S. Diplomat's wife who fled the countryTo learn more about how CNN protects listener privacy, visit cnn.com/privacy Learn more about your ad choices. Visit podcastchoices.com/adchoices