US Ambassador to the United Nations Samantha Power announces the start of the #FreeThe20 campaign from the State Department September 1, 2015 in Washington, DC. (Photo by Chip Somodevilla/Getty Images)

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Susan Rice had been scheduled to speak to the panel Tuesday

Samantha Power served as the US ambassador to the United Nations under Obama

CNN  — 

The House intelligence committee has delayed classified testimony expected this week from former Obama national security adviser Susan Rice as the panel is now working to bring forward another former Obama official as soon as this month: Samantha Power.

Power, who like Rice also served as the US ambassador to the United Nations under Obama, has agreed to come before the committee, sources say. The panel is still finalizing a date, but her testimony could occur before the August recess.

Republicans have pushed to bring Power and Rice before their committee in a bid to learn whether they improperly “unmasked” – or revealed the identities typically blacked out in intelligence reports – of Trump associates. But Democrats have scoffed at the GOP push, a sign of the partisan strife that still exists over the direction of the committee’s probe into alleged Russia’s interference in the US elections.

According to sources familiar with the matter, Rice had been scheduled to speak to the panel Tuesday, but the committee has delayed her testimony for a later date. Rice, who has strongly denied any wrongdoing, declined to comment through a spokesperson, but is still expected to come before the panel at some point. Power has repeatedly called for an investigation into alleged Russian interference in the election, and has expressed a willingness to cooperate.

The delay of Rice’s testimony would amount to at least the third time the panel has pushed back a scheduled witness’ testimony. It also delayed hearing from Trump associate Roger Stone and former adviser J.D. Gordon. The GOP leader of the House Russia probe, Mike Conaway, said last week that the investigation is going “frustratingly slow.”

“We’re all in this instant gratification world that we’ve created for ourselves and the fact that it takes response times, you get lawyers involved, back and forth organizing – that’s frustrating,” Conaway said.

The top Democrat on the panel, Rep. Adam Schiff, said: “Our decisions on scheduling are made based on what’s best for the investigation – not based on what’s best for any particular witness.”

Representatives for Conaway and Schiff could not be reached for comment about the Rice and Power testimony.

The committee’s chairman, Devin Nunes, who stepped aside from leading the Russia probe amid a cloud of controversy, led a push to issue subpoenas earlier this year to learn about unmasking requests related to Rice, Power and former Obama CIA Director John Brennan.

David Pressman, a counsel to Power, said that the former UN ambassador planned to fully cooperate with the panel’s investigation into Russia interference.

“Ambassador Power strongly supports any bipartisan effort to investigate and address Russia’s interference in our electoral process and she wanted to engage both the House and Senate Committees charged with investigating it,” Pressman said. “Long before receiving an invitation to engage the congressional committees, Ambassador Power stressed the importance of determining the full extent of this threat to our national security and learning lessons from what has happened.”

This story has been updated.