President-elect Joe Biden is taking aim at President Trump for refusing to concede the election and stalling the transition between adminstrations, saying he is being “totally irresponsible” and is sending an “incredibly damaging message” to the rest of the world.

Biden, while taking questions from reporters Tuesday after he and Vice President-elect Kamala Harris held a virtual meeting with a bipartisan group of governors, also revealed that he's decided on a Treasury secretary nominee and will make the announcement around Thanksgiving.

The president-elect called his choice “someone who I think will be accepted by all elements of the Democratic Party, from the progressive to the moderate coalitions."

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Asked about the president’s invitation for a meeting with Republican legislative leaders from Michigan at the White House, Biden emphasized, “we won Michigan. It’s going to be certified.”

Trump is trying  to reverse Biden’s projected victories in that state and other key battlegrounds. Biden stressed, “it’s outrageous what he’s doing.”

President-elect Joe Biden and Vice President-elect Kamala Harris participate in a meeting with the National Governors Association's executive committee at The Queen theater, Nov. 19, in Wilmington, Del. (AP Photo/Andrew Harnik)

The Biden-Harris meeting with the governors focused on the battle to combat the coronavirus pandemic, which has surged again across the nation in recent weeks with a spike in new cases. The nation passed a grim milestone  Wednesday, topping a quarter of a million COVID-19 deaths since the pandemic swept the country in February and March.

Biden said that an “implementation of a national mask mandate” was discussed. “It’s not a political statement. It’s a patriotic duty.”

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The meeting took place as Republican Gov. Chris Sununu of New Hampshire became the latest governor to issue a mask mandate. New Hampshire became the 37th state implementing such a mandate.

The president-elect also reaffirmed, “I am not going to shut down the economy. Period. I’m going to shut down the virus. That’s what I’m going to shut down. I’ll say it again - no national shutdown. No national shutdown.” He added that shutting down the economy “would be counterproductive."

Fox News, other news networks and the Associated Press, projected nearly two weeks ago that Biden would win the state of Nevada and the commonwealth of Pennsylvania, which would give the Democratic presidential nominee the electoral votes needed to defeat Trump and become president-elect. But Trump has yet to concede, as he hopes that a spate of apparent longshot lawsuits he’s filed and a couple of recounts in key states will reverse Biden’s victory.

The president on Sunday tweeted, "I concede NOTHING! We have a long way to go." And on Monday the president claimed on Twitter that “I won the Election!” On Wednesday he reiterated on Twitter that “I WON THE ELECTION” and charged that there was “VOTER FRAUD ALL OVER THE COUNTRY!”

General Services Administration chief Emily Murphy, who was appointed by Trump, has yet to sign a letter of “ascertainment,” which until now was a mostly controversy-free process of declaring the winner of the White House race. The document gives the president-elect's transition team access to the federal agencies and money to fund the transition.

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Biden said the world was "witnessing incredible irresponsibility" by the president. He charged that "an incredibly damaging message is being sent to the rest of the world about how democracy functions." 

Pointing to Trump, he said "I don’t know his motive but I think it’s totally irresponsible."

But the president-elect added he wasn't concerned that Trump would succeed in having people question the legitimacy of his administration. Biden pointed to new public opinion polling this week that indicated a majority of Americans think the election results are legitimate.

"Most of the Republicans I’ve spoken to, including some governors, think this is debilitating. It sends a horrible message about who we are as a country," Biden said.

Biden also once again chastized the president and his adminsitration for failing to give any access to Biden and his growing team of advisers and aides to goverment agencies and officials. That's prevented Biden from receiving intelligence briefings or obtaining the latest COVID data and plans for vaccine distribution.

"There is no excuse not to share the data and begin to plan because on day one it’s going to take us time if we don’t have access to all this data," Biden said. "It’s going to put us behind the 8-ball by a matter of a month or more. And that’s lives. How many would be lost as a consequence of that, I can’t tell you."

Asked if he's contemplating legal moves to force the adminstration to recognize his election victory, or to push back against Trump's efforts to overturn the election results, Biden said, "I’m not going to rule anything out or anything in, but at the moment our strategy is not changing."

But Biden said that Trump's efforts to question the election results is "going to be another incident where he will go down in history as being one of the most irresponsible presidents in American history."

"It’s hard to fathom how this man thinks," Biden added. "It’s hard to fathom. I’m confident he knows he hasn’t won and is not going to be able to win and we’ll get sworn in on Jan. 20."

Vice President-elect Kamala Harris, accompanied by President-elect Joe Biden, speaks at The Queen theater, Thursday, Nov. 19, 2020, in Wilmington, Del. (AP Photo/Andrew Harnik)

Biden and Harris, who gathered in the former vice president's hometown of Wilmington, Del., met virtually with the bipartisan leadership of the National Governors Association (NGA).

The group included Democratic Gov. Andrew Cuomo of New York and Republican Gov. Asa Hutchinson of Arkansas, the current NGA chair and co-chair.

Also taking part in the meeting were Republican Govs. Charlie Baker of Massachusetts, Gary Herbert of Utah, Larry Hogan of Maryland and Kay Ivey of Alabama, and Democratic Govs. Michelle Lujan Grisham of New Mexico, Jared Polis of Colorado, Gretchen Whitmer of MIchigan, and John Carney of Delaware.

Harris said that she told the governors "they will have partners in the White House starting on Jan. 20."

And the senator from California added that "our message to our governors and all of our nation’s state and local leaders is simple – President-elect Biden and I will make sure you have the resources and support you need to save lives and help get our economy back on track."

On Friday, Biden and Harris will meet in in-person in Wilmington with the top two Democrats in Congress - House Speaker Nancy Pelosi and Senate Minority Leader Chuck Schumer.

Fox News' Tara Prindiville and Madeleine Rivera, Mike Emanuel, Peter Doocy, and Patrick Ward contributed to this report