Biden is expected to name former Federal Reserve Chair Janet Yellen as his pick for treasury secretary sources familiar with the matter told ABC News. Yellen, would be the first woman to serve in the role if confirmed.

As Biden signaled when announcing he had made a decision on who would fill the role, the choice of Yellen is likely to earn approval from progressive Democrats like Sen. Elizabeth Warren, D-Mass., who previously supported Yellen for chair of the Federal Reserve in 2013. In the last few days, leaders of progressive organizations have already signaled that should Warren not be slated for the role, Yellen would be acceptable in their minds.

ABC News has reached out to the Biden transition team for comment. The news was first reported by the Wall Street Journal.

-ABC News' Martha Raddatz, Katherine Faulders, John Santucci and Molly Nagle

Two House committees continue to battle with the General Services Administration over Administrator Emily Murphy's refusal to formally acknowledge the results of the election, which has stymied President-elect Joe Biden's transition process.

The Committee on Oversight and Reform and the Appropriations Committee have rejected an offer from the GSA to have Murphy's deputy brief lawmakers next week, following an initial request for Murphy to brief lawmakers by Monday.

"We cannot wait yet another week to obtain basic information about your refusal to make the ascertainment determination," top Democrats said to Murphy in a written response. "Every additional day that is wasted is a day that the safety, health, and well-being of the American people is imperiled as the incoming Biden-Harris Administration is blocked from fully preparing for the coronavirus pandemic, our nation’s dire economic crisis, and our national security."

Democrats have offered to host the briefing themselves.

Murphy's office claimed the briefing had to be moved to next week because of the closure of the GSA office due to "threatened violence against the facility."

A GSA spokesperson did not respond to ABC News' request for comment.

-ABC News' Benjamin Siegel and Anne Flaherty

Michigan election officials are in the process of determining whether to certify the state's election results amid GOP efforts to delay it. Trump is currently trailing Biden by more than 150,000 votes.

If the state board, comprised of two Republicans and two Democrats, is deadlocked in its vote, the Michigan Court of Appeals would intervene and likely compel certification.

The Republican vice chair of the board of state canvassers, Aaron Van Langevelde, said the board’s duty is “very clear.”

“We have a duty to certify the selection based on the returns," he said, opening the meeting to public comments. "That is very good. And we are limited to these returns, and I'm not going to argue that we're not, but I still think that people have signed up today did have a chance to speak before we act on this motion."

The board’s other Republican member, Norm Shinkle, told the Washington Post last week he is leaning toward delaying certification.

At least three votes are needed for certification.

-ABC News' Kendall Karson

Shortly before the president-elect officially announced his picks for foreign policy and national security, former President Barack Obama weighed in with praise for the development of a team he said he has confidence in.

Obama described Antony Blinken, who was Obama's deputy national security adviser and Biden's foreign policy adviser when he was vice president, as a trusted adviser and a skilled diplomat. Blinken was tapped for secretary of state.

"He was part of our inner circle in on our key meetings throughout my presidency. He's outstanding, a smart, gracious skilled diplomat, well regarded around the world, and I know he's going to do a great job," Obama said during a Washington Post Live event.

Obama called Jake Sullivan, Biden's pick for national security adviser, a "wicked, smart, young, energetic" and "outstanding" selection.

"So you're seeing a team develop that I have great confidence in," Obama said, before cautioning that restoring allies' confidence in the U.S. will not be "restored overnight."

"There is going to be a lingering sense that America still divided. Some of the shenanigans that are going on right now around the election, that is making the world question how reliable and steady the U.S. may be," Obama said. "There's been some damage done that is going to take some time to dig ourselves out of."

-ABC News' Jordyn Phelps

Retired Navy Adm. William McRaven said Sunday that he doesn't think the president-elect can get back into the Iran nuclear deal without some changes.

"There's been a lot of controversy and a lot of folks who don't like the JCPOA and I understand that," McRaven said on ABC's "This Week." "But the fact of the matter is the JCPOA, which probably going to give us, you know, 10 to 12 to 15 years before the Iranians could possibly have enriched enough uranium to build bomb."

Complicating matters is Friday's apparent assassination of one of Iran's most prominent scientists, Mohsen Fakhrizadeh. While no one has claimed responsibility for the killing, the incident has brought out a full response from Iran's top officials, including the country's foreign minister, Mohammad Javad Zarif, who pointed the finger at Israel.

"Now, of course, by attacking their nuclear scientist, by really escalating this effort, the Iranians I think are going to be more compelled to try to get a bomb quicker. This is going to complicate President Biden's efforts, diplomatic efforts," he told "This Week" Co-anchor Martha Raddatz on Sunday. "Now, again, from the Iranian standpoint, after President Trump pulled out of the JCPOA, I think they are going to be very, very reluctant to get into any agreements with the United States at this point. So, a President Biden will have a difficult challenge on his hand."