US House Intelligence Committee Chairman Adam Schiff has announced that federal law enforcement agencies might be withholding evidence pertinent to US President Donald Trump’s impeachment trial.

Trump is to be tried for secretly holding up $391 million in aid to Ukraine between July and September to pressure Kiev to investigate former vice president Joe Biden, the Democratic frontrunner in this year’s White House race. The president is also charged with obstruction for holding back witnesses and documents from the House impeachment investigation in defiance of Congressional subpoenas. He was formally impeached on December 18.

NSA and CIA appear to be succumbing to pressure from the administration, Schiff, who was chosen by House Speaker Nancy Pelosi as the lead manager for Trump’s impeachment trial, told ABC’s This Week″ program, on Sunday.

Schiff noted that the NSA, in particular, was withholding what are potentially relevant documents to our oversight responsibilities on Ukraine. Schiff pointed out that the intelligence community needed to work with lawmakers if they were to gain the power to find the truth behind the Ukraine scandal.

A member of the intelligence community’s public relations apparatus responded to Schiff’s demands, assuring him and other members of Congress that the intelligence community would work with lawmakers to empower them to carry out their oversight obligations.

The intelligence community is committed to providing Congress with information and intelligence it needs to carry out its critical oversight role, Amanda Schoch, assistant national intelligence director for strategic communications, said in a statement Sunday, adding,The intelligence community is working in good faith with the House Permanent Select Committee on Intelligence to respond to requests on a broad range of topics and will continue to do so.