Washington: Lawmakers of both parties have expressed outrage over the Trump administration's decision to make a deal relaxing penalties imposed on Chinese telecom giant ZTE for violating US sanctions against exporting to Iran and North Korea.

They included language with bipartisan backing in a defence policy bill now pending before the Senate to re-impose the penalties and ban US government agencies from purchasing any devices or services from ZTE.

Now the White House is defending its decision to lift restrictions against ZTE - and suggesting that congressional attempts to intervene violate the constitution's separation of powers.

In April the Commerce Department announced the telecommunications giant would be banned for seven years from buying critical parts from American firms after the company sold items to Iran and North Korea in violation of a sanctions settlement. But President Trump decided to back off that punishment, after Chinese leaders said it would drive the company out of business.