North Korea on Friday threatened to resume development of nuclear weapons if the United States does not lift economic sanctions.

"The U.S. thinks that its oft-repeated 'sanctions and pressure' leads to 'denuclearization,'" said a statement from Pyongyang. "We cannot help laughing at such a foolish idea." The statement argued lifting sanctions would be an appropriate reciprocation of North Korea's "proactive and good-will measures" since opening denuclearization talks with the U.S. and South Korea.

Also Friday, Secretary of State Mike Pompeo indicated sanctions will continue. "A lot of work remains," he said, "but I'm confident that we will keep the economic pressure in place until such time as [North Korean leader Kim Jong Un] fulfills the commitment he made to President Trump back in June in Singapore." Bonnie Kristian

It's not former Vice President Joe Biden's first time on the presidential train. But seeing as he's safely boarded — albeit a bit late — for 2020, let's take a look back at his past journeys.

Biden's first bid was for the 1988 presidential race and, in no surprise given his Amtrak obsession, he revealed it in a June 1987 speech in Wilmington, Delaware's train station.

Yet Biden failed to keep his run on the rails, and hopped out of the contenders' car just a few months later.

As promised in that 1988 speech, there were "other presidential campaigns," namely 2008's. Biden formally revealed his run in a Jan. 31, 2007 Meet the Press appearance, and followed it up with a video on his website.

Biden's withdrawal from the race didn't come until nearly a year later after rolling into fifth place in the Iowa caucus, and he made that choice in a small speech to supporters and staffers. Of course, Biden still ended up in the White House, becoming former President Barack Obama's running mate at this Aug. 23, 2008 event in Illinois.

Compare these past announcements to Biden's 2020 video here. Kathryn Krawczyk

Former Vice President Joe Biden says he didn't even want former President Barack Obama's endorsement, anyway.

After Biden officially announced his presidential campaign on Thursday, an Obama spokesperson released a statement praising his "knowledge, insight, and judgment." But it stopped short of an endorsement, and CNN's Jeff Zeleny reported Obama is unlikely to endorse because he would prefer "to let the candidates make their cases directly to the voters."

Obama last election cycle endorsed Hillary Clinton in June 2016, one month ahead of the Democratic National Convention. In February, The New York Times reported that Biden and his allies don't expect Obama to endorse him or any other candidate in the 2020 Democratic primary, and that former first lady Michelle Obama is also unlikely to do so.

Asked about this lack of endorsement, Biden said on Thursday that he actually asked Obama not to do so. "I asked President Obama not to endorse," he said, CNN reports. "Whoever wins this nomination should win on their own merits." Brendan Morrow

Did you know Joe Biden takes the Amtrak?

Just a few hours after the former vice president announced his candidacy for president, he was already spotted back aboard his favorite mode of transportation. America's top train line has been as constant in Biden's life as presidential campaigns, and, unsurprisingly, it's already a big part of his 2020 one.

Biden got his public transportation reputation back in his senatorial days, riding the train back and forth between his family in Delaware and Capitol Hill every day. He even took the Amtrak home after President Trump's inauguration in 2017. Now, the train has yet again pulled back into Biden's station, both in reality and in a very prominent place on Biden's campaign website. Kathryn Krawczyk

Fox News legal analyst Andrew Napolitano is blasting President Trump over Special Counsel Robert Mueller's report, suggesting it proves he obstructed justice numerous times.

In an op-ed for Fox News, Napolitano wrote that Mueller's report includes "at least a half-dozen crimes of obstruction committed by Trump," including Trump allegedly asking his White House counsel to fire Mueller, something Trump has denied doing. "That's obstruction of justice," Napolitano definitively and repeatedly states in a video after running through a number of incidents described in the Mueller report.

The Fox News analyst ripped into the president for this behavior, writing, "ordering obstruction to save himself from the consequences of his own behavior is unlawful, defenseless and condemnable."

Napolitano also takes issue with Attorney General William Barr, saying he's "wrong" to say a person can't be guilty of obstruction if they aren't guilty of the underlying crime being investigated. Instead, Napolitano says, the "nearly universal view of law enforcement" is that any attempted interference with an investigation is obstruction, and the obstruction doesn't have to be successful to be unlawful.

Napolitano summarized the situation in a video, saying the report concludes that Trump "probably committed the crimes of obstruction of justice but probably should not be charged for them," which he calls a "head-scratcher." The question now, Napolitano writes in his op-ed, is whether Democrats will "utilize Mueller's evidence of obstruction for impeachment." Brendan Morrow

Joe Biden is already proving President Trump's "Sleepy Joe" nickname wrong.

After months of teasing, the former vice president launched his presidential campaign on Thursday with a video tweeted at an absurdly early 6:00 a.m. EST. Sure, most of America was probably still in bed, but that's just what makes Biden's timing a shrewd, agenda-setting move.

With reports already indicating that Biden would announce Thursday, it made sense that he would ditch any pretenses and get the big news out first thing. That timing meant Biden dominated news alerts and publications' morning newsletters, and that he secured a top trending spot on Twitter even as the Midwest was still waking up. It also meant Biden slid right into Trump's typical morning tweetstorm, which suggests the president sees him as a threat. Perhaps Biden even took a cue from Trump in that respect, seeing as what the president tweets during his early executive time often dominates the news cycle all day.

Before Biden, Sen. Bernie Sanders (I-Vt.) had the earliest announcement video drop at 7:02 a.m EST. He's also — though probably unrelatedly — falling into second place behind Biden in most polls. Sens. Cory Booker (D-N.J.), Elizabeth Warren (D-Mass.), and Kamala Harris (D-Calif.) also shared announcement videos in the 7 a.m. hour. Sen. Amy Klobuchar (D-Minn.) and Pete Buttigieg, meanwhile, gave in-person speaking announcements in reasonable mid-afternoon time slots.

Sen. Kirsten Gillibrand (D-N.Y.) and Rep. Eric Swalwell (D-Calif.) secured some of the latest announcement times, both revealing their runs around 7 p.m. EST on The Late Show with Stephen Colbert. Former congressmember Beto O'Rourke also came in pretty late, spoiling his formal morning announcement with a text to a TV station the night before. Maybe, just maybe, that could play into why his campaign has stalled in the month since. Kathryn Krawczyk

Will the media make the same mistake with Joe Biden as it did with President Trump in 2016?

FiveThirtyEight's Nate Silver wondered as much on Thursday after Biden officially entered the 2020 race. The statistician and election expert writes that "there's a case to be made" that the media is "overlooking the obvious front-runner in Biden," instead chasing "shiny new objects like Pete Buttigieg" and ignoring "older, more working-class and more moderate Democrats."

Silver suggests media elites might have the "same blind spots for Biden that they had for Trump," meaning that although "journalists' social circles" may not be chock-full of Biden voters, "that doesn't mean they aren't out there." The fact that Biden's poll numbers have been largely unaffected by accusations of inappropriate touching also suggests "it's possible that the media is underestimating how robust Biden's support might turn out to be," Silver says.

This isn't to say that Silver sees Biden as a shoo-in for the Democratic nomination, though. He refers to Biden as an "underdog" in the field and points out a number of potential liabilities, including his age. Unfriendly media coverage could also hurt Biden, Silver believes, as his candidacy will be seen within the mainstream media as "boring and anticlimactic."

Still, Silver assesses that while Biden is not the "odds-on favorite," he is the race's front-runner, and he has clear paths to the nomination before him. Read Silver's analysis of Biden's 2020 chances at FiveThirtyEight. Brendan Morrow