WASHINGTON – Special counsel Robert Mueller appears to be interested in talking to current and former White House officials as part of his ongoing federal Russia investigation – and his list of potential witnesses is long.

President Trump's aides could provide information that may prove relevant to Mueller's investigation into contacts between Trump associates and Russians who sought to influence the election by hacking Democrats close to candidate Hillary Clinton. Mueller's office is also investigating possible obstruction of justice – a front opened after the president abruptly fired FBI Director James Comey in May for his handling of the Russian investigation.

White House officials have pledged to cooperate with Mueller's office, including by producing documents his team has requested, but would not share any names the special counsel was seeking. "The White House, out of respect for the Special Counsel and his process, will not be commenting on specific requests received from the Special Counsel," White House attorney Ty Cobb said Thursday.

While there is not yet evidence Mueller is seeking to talk to Trump himself, people familiar with the investigation believe the special counsel may be interested in interviewing a number of the president's current and former aides.

Among them:

Former White House Chief of Staff Reince Priebus

Investigators may want to talk to Priebus, who left the White House in late July, about a February conversation he had with with Comey. Priebus asked Comey to get the FBI to publicly condemn a news report claiming that Trump advisers had contacts with Russian officials during the presidential campaign. Comey and his then-deputy Andrew McCabe declined to do so.

After Trump dismissed him, Comey said the president had asked him to drop at least part of his investigation into former National Security Adviser Michael Flynn and contacts he made with then Russian ambassador Sergey Kislyak. Priebus, who was chief of staff during all of these exchanges, would have likely been familiar with Trump's meetings with Comey.

Donald Trump Jr.

The president's son, who was also involved in Trump's campaign, testified this week about his 2016 meeting with a Russian lawyer whom he believed had damaging information about Clinton. Participants in the meeting said no such information was ever produced, and the younger Trump denied any wrongdoing in testimony this week to Senate investigators.

Interim White House Communications Director Hope Hicks

Hicks worked with Trump on Donald Trump Jr.'s initial statement about the Trump Tower meeting. Investigators want to know if that statement – which was later proved to be incomplete and misleading – constituted an effort to obstruct justice.

White House officials said Trump made only a few suggestions regarding his son's statement. "The President weighed in as any father would, based on the limited information that he had," said White House spokeswoman Sarah Sanders in August.

Former Press Secretary Sean Spicer

During the post-election presidential transition, Spicer told reporters that then-national security adviser Michael Flynn did not discuss pending economic sanctions on Russia in a post-election phone call with Sergey Kislyak, the Russian ambassador.

Flynn later said the topic could have come up. White House officials later said that Flynn misled several colleagues, including Vice President Mike Pence, and that is the reason Trump fired him.

White House counsel Don McGahn

The Washington Post reported that Mueller has also notified the White House that "he will likely seek to question" McGahn and one of his deputies, James Burnham.

In January, just days before she was fired as acting attorney general, Sally Yates was so troubled that Flynn misled his colleagues about his communications with the Russian ambassador that she warned McGahn, telling him the then-national security adviser was vulnerable to blackmail and could even face criminal charges. While Yates told a congressional panel in May that McGahn asked her whether Flynn should be immediately dismissed, he was only let go weeks later after news reports exposed details of his contacts with the Russian ambassador.

The Post noted that "courts have held that the president does not enjoy attorney-client privilege with lawyers in the White House Counsel’s Office and their testimony about their Oval Office dealings can be sought in investigations."

Senior adviser and Trump son-in-law Jared Kushner

Kushner was heavily involved in the presidential campaign. In recent congressional testimony, Kushner denied any involvement with Russians during the election year. Kushner attended the 2016 meeting with a Russian lawyer, and also had contact with Kislyak during and after the campaign. Kushner's congressional testimony is already available to investigators.