WASHINGTON (Reuters) - Talks over whether the whistleblower who sparked an impeachment inquiry into U.S. President Donald Trump will testify to Congressional committees are hung up on the question of whether the person can submit written testimony, two sources familiar with the discussions said.

Negotiators in the Democratic-led U.S. House of Representatives are open to the career intelligence officer making written testimony while negotiators in the Republican-majority Senate have resisted, said the sources.

The whistleblower’s representatives want to make sure the person remains anonymous. Discussions between Congressional investigators and representatives of the whistleblower have been suspended at least temporarily, though the sources indicated they were expected to resume when lawmakers return from a recess next week.

Representatives of the committees had no immediate comment.

Democrats began the impeachment inquiry of Republican Trump on Sept. 24 following the revelation that a whistleblower had lodged a complaint about a July 25 phone call in which Trump pressed Ukrainian President Volodymyr Zelenskiy to investigate former U.S. Vice President Joe Biden, a leading Democratic contender for the right to face Trump in the November 2020 election.

Democrats have accused Trump of pressuring a vulnerable foreign ally to dig up dirt on a domestic political opponent for his own political benefit. Trump has denied he did anything wrong on the call.

A source familiar with arguments the whistleblower’s representatives have been making to Congressional interlocutors said that the whistleblower’s view is that the three Democratic-led House committees - Intelligence, Oversight and Judiciary - and the Senate Intelligence Committee should treat any appearance by the person in identical fashion.

On Friday, the former U.S. ambassador to Ukraine, Marie Yovanovitch, told the impeachment inquiry that Trump ousted her abruptly in May based on “unfounded and false claims” after she had come under attack by his personal lawyer Rudy Giuliani.