United States President Donald Trump's lawyers are now saying that his move to put pressure on Ukraine in exchange for military aid is because he wanted to unearth a corruption scandal.

The impeachment trial continues as the question of whether more witnesses will be called on remains unresolved.

Democrats want former National Security Advisor John Bolton to testify, but if they fail to persuade the Senate to vote for that move on Friday, the trial could end with a vote to acquit Trump.

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