Attorney General William Barr still believes special counsel Robert Mueller should be allowed to testify before Congress, despite President Donald Trump’s apparent objection, according to a source familiar with the attorney general’s thinking.

As the head of the Justice Department and Mueller’s boss, Barr could attempt to block the testimony if he chooses.

The president’s tweet over the weekend raised questions about whether he was instructing Barr to stop the special counsel’s requested testimony from happening.