WASHINGTON - The prospects of Ms Kathleen Troia "K.T." McFarland's confirmation as US ambassador to Singapore are looking grim, according to a CNN report.

This is as questions continued to be raised over whether she properly disclosed to Congress her communications with former national security adviser Michael Flynn, CNN reported on Wednesday.

Lawmakers and senior aides told CNN they expect the Senate to send her nomination back to the White House when this year's session takes a recess at the end of the week.

Ms McFarland, 66, previously served as Mr Flynn's deputy. She came under the spotlight earlier this month after Mr Flynn's plea agreement with Justice Department special counsel Robert Mueller appeared to be at odds with her testimony to Congress.

Senate Foreign Relations chairman Bob Corker, whose committee oversees the McFarland nomination, told CNN that the Senate plans to send her nomination back, adding that the White House "will have to make decisions on whether they renominate" her.

"Nominees that have other productive lives they can lead probably have to assess themselves whether it makes a lot of sense to continue on because it does put your life on hold," CNN quoted him as saying. "Before any of these other things came out, there were significant Democratic objections to this nominee - the nominee is aware of that. This obviously makes it more difficult."

In order to be confirmed, Ms McFarland will need support from Senate Democrats to expedite a vote. But Democratic officials say it is not going to happen, said CNN.

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"No chance she gets confirmed by year's end," a Senate Democratic leadership aide said.

The controversy surrounding Ms McFarland's nomination ignited earlier this month after court documents showed that Mr Flynn spoke to a senior transition team official about what to discuss with then Russian ambassador Sergey Kislyak after the Obama administration issued new sanctions against Russia on Dec 29 last year.

While Ms McFarland was not mentioned in the court papers, US media reports identified her as the transition team official.

Ms McFarland had told the Senate Foreign Relations Committee in September that she "was not aware" of any communication between Mr Flynn and Mr Kislyak.

The majority of US ambassadors posted overseas are career State Department officials. In recent years, about 30 per cent of them were political appointees, posted especially to countries with which Washington has significant ties.

US ambassadors to Singapore have been political appointees since veteran diplomat J. Stapleton Roy left in 1986.