President Donald Trump is claiming he wants top aides to testify in his Senate impeachment trial, but he qualifies that by suggesting there are “national security” concerns about allowing their testimony. Trump spoke to reporters Wednesday at a global economic forum in Davos, Switzerland. Senate Republicans have for now blocked Democratic motions to immediately call witnesses and subpoena documents. On Tuesday, the Senate approved rules for Trump’s trial on two articles of impeachment. Democrats failed to persuade Republicans to agree to issue subpoenas for documents and witnesses, though those matters can be revisited later.