A bid to call a former US national security advisor before President Donald Trump’s impeachment trial has been blocked by Republican Senators.

In an early illustration of the partisan nature of the impeachment procedure, The Republican-controlled Senate rejected a number of Democratic bids to call witnesses and subpoena White House documents for the trial.

The Senate voted against compelling President Trump’s former national security advisor John Bolton to testify along with former White House chief-of-staff Mick Mulvaney.

Mr Bolton who was sacked from his position in September had previously indicated that he would testify in the trial if he was compelled to.

Meanwhile, the Senate rejected bids to subpoena documents from the White House, State Department, Defence Department and Budget Office.

It also voted to delay a debate on whether to call witnesses until the middle of the trial.

The senators voted along party lines in the votes, with the Republicans winning by a 53-47 margin.

Senate Democratic leader Chuck Schumer accused Republican senators of “enabling a cover-up.”

President Trump is charged with abuse of power and obstruction of Congress.

He is accused of freeze Congress-approved aid to Ukraine in a bid to pressure the country’s president to open up an investigation into Democratic presidential hopeful Joe Biden – and impeding an investigation into the accusations.

The final impeachment vote in the Senate, which will decide whether Mr Trump is guilty, is expected to be along party lines and it is therefore unlikely the president will be removed from office.

Additional reporting from IRN