US House Speaker Nancy Pelosi and Senate Majority Leader Mitch McConnell sparred on Monday over the ground rules for President Donald Trump’s trial in the Senate on charges of abuse of power and obstruction of Congress.

Pelosi, the speaker of the Democratic-controlled House of Representatives, said she is not yet ready to name her team for Trump’s trial in the Republican-majority Senate.

House managers will prosecute the case against Trump in the Senate in a trial expected to begin in January. Trump’s Republicans have a 53-47 seat edge in the chamber.

Pelosi has not yet sent the impeachment articles passed by the House last week over to the Senate amid a standoff with McConnell over the form the trial will take.

Democrats have been pushing for four current and former White House aides with direct knowledge of Trump’s Ukraine dealings to testify in the Senate. Trump blocked all four from testifying in the House.

“President Trump blocked his own witnesses and documents from the House, and from the American people, on phony complaints about the House process,” Pelosi said. “What is his excuse now?”

McConnell, speaking on the Fox & Friends television show on Monday, said Pelosi “apparently believes that she can tell us how to run the trial.” McConnell chided Pelosi for not sending the articles over to the Senate yet.

The House voted along party lines last week to impeach Trump for abuse of power for pressuring Ukraine’s president to investigate his potential 2020 election opponent, Democrat Joe Biden. Trump is accused of withholding military aid to Ukraine to push Kiev to investigate Biden.