Former Secretary of State John Kerry was forced to knock down a 'f***ing' false report that he might run for president after he was overheard in an Iowa hotel lobby talking about contingencies if Bernie Sanders prevails.

Kerry issued a stunning denial on Twitter – first dropping an f-bomb and then removing it – to cast aside a report on his supposed plans. He is here in Iowa stumping for former Senate colleague Joe Biden, who is desperately trying to head off a Sanders insurgency.

'As I told the reporter, I am absolutely not running for President. Any report otherwise is f***ing (or categorically) false,' Kerry said in a now-deleted tweeted. 'I've been proud to campaign with my good friend Joe Biden, who is going to win the nomination, beat Trump, and make an outstanding president.'

Former Vice President Joe Biden (R) hugs former Secretary of State John Kerry (L) as Biden campaigns to be the 2020 Democratic presidential nominee at the Roosevelt Creative Corridor Business Academy in Cedar Rapids, Iowa, USA, 01 February 2020. Kerry was overheard in an Iowa hotel lobby discussing the possibility of Bernie Sanders 'taking down' the Democratic Party

Kerry issued two tweets denying the story – the first using profane language, the second without it

He was responding to an NBC News report about one end of a phone conversation overheard in a downtown Des Moines hotel.

A network analyst who overheard him said Kerry spoke about 'the possibility of Bernie Sanders taking down the Democratic Party — down whole.'

The purported statement speaks to the concern with which many party heads fear Sanders, a self-described Democratic socialist who touts a variety of proposals that he describes as progressive but President Trump is certain to paint as socialist.

Some party stalwarts fear a Sanders win and what it might do to the party's chances against Donald Trump, who squeaked out an Electoral College win over Hillary Clinton despite losing the popular vote.

'Maybe I'm f---ing deluding myself here' Kerry was heard explaining.

He said he would have to step down from the board of Bank of America and relinquish the paid speaking circuit – which proved damaging to 2016 nominee Hillary Clinton. He even mentioned a donor who would need to 'raise a couple of million.

The 2004 Democratic presidential nominee is in Iowa campaigning for Biden – and he is one of the former vice president's highest profile endorsers.

At a campaign even in North Liberty, Iowa, on Saturday, Kerry spoke after Biden's remarks for a longer time than the candidate.

Former Sen. John Kerry's original tweet was captured by reporters. He later deleted it for a cleaner version

I COULD DO THIS: Kerry forcefully denied he was considering a run

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When asked by NBC, Kerry denied he was considering running.

He said he was 'absolutely not' thinking about getting into the primary. Some states have already closed their registration deadline, as candidate Michael Bloomberg had to contend with in his own late entry.

Bloomberg announced his candidacy in late November, and is the most recent to join the race. There are now only 11 candidates in the still-thinning field that once featured 28 candidates.

Last month NBC asked Kerry if he regretted not entering the 2020 race.

'I'd be a liar if I didn't say I don't come out here and have fun and your juices don't get going,' he said at the time.

'But right now, they're entirely focused on helping Joe Biden become president, and I'm very happy doing what I'm doing,' he continued.

Kerry's new overheard comments come at a time of tension and concern within the party about what will happen if Sanders wins, or how Sanders' legions of young and left-wing supporters will respond if he is denied the nomination.

No matter if the conversation was more jest than serious, it shows that Kerry has concerns with Biden's chances ahead of the Monday first-in-the-nation primary caucus in Iowa.

Sanders has been drawing crowds in the thousands over the weekend in Iowa cities, while Biden has held smaller events.

A number of recent polls have shown Biden and Sanders neck-and-neck in the Hawkeye State.

Rep. Ro Khanna, a California Democrat who co-chairs Sanders' campaign, told DailyMail.com that he didn't believe the NBC report.

'I don't believe it. I think it's media generation,' Khanna said outside of Sanders' Super Bowl gathering in Des Moines Sunday night. 'He's been a great statesman on climate change and it's a media-generated story. He has no interest in running.'

The congressman pointed out that he and Kerry had co-authored an op-ed in December for The New York Times, and he didn't detect any anti-Sanders sentiment then.

'I think this is a media fabricated story. I know John Kerry well. I think the world of him. He co-authored an op-ed with a national Bernie co-chair,' Khanna said.

He answered 'not at all' when asked if he thought there was any way Kerry would try to sabotage the Sanders campaign if the Vermont senator were to win the Democratic nomination.

Sanders ignored a question about Kerry from DailyMail.com outside his Super Bowl shindig.