NEW YORK - Hillary Rodham Clinton met Wednesday with London mayor Boris Johnson -- a man who once described her both as a scary nurse in a mental ward and a woman who represented "on the face of it, everything I came into politics to oppose."

Johnson is widely considered a likely candidate for prime minister in the not-too-distant future, meaning it’s possible that he and Clinton could be stewards of their nations' vaunted "special relationship" at the same time.

Before arriving in New York Tuesday on a trade mission, Johnson somewhat sheepishly told the BBC that he was sure Clinton would take his 2007 Daily Telegraph column in the “lighthearted” spirit in which it was intended.

On Wednesday, Clinton playfully mocked Johnson’s ambitions -- and perhaps her own -- as she arrived for their meeting.

“Is he announcing for president?” she quipped to British reporters. “Which one do you think he'll be, Democrat or Republican?’”

“Just met w/@HillaryClinton for talks on security, the threat of ISIL returnees & the synergy between London & NYC,” Johnson tweeted afterward.

(Note to @mayoroflondon: Please tweet any really good zingers she got off during the meeting. Also anything about when she's actually announcing her campaign. Thank you.)

Johnson is in New York as part of a week-long trade mission that also includes stops in Boston and Washington. His meeting with Clinton was closed to the press, although cameras caught her arrival. Clinton’s spokesman declined to comment on the purpose. Or even the time and place.

Johnson was a member of parliament when he wrote the 2007 column about Clinton, then a New York senator and U.S. presidential aspirant. He went on to become mayor in 2008; she went on to lose the Democratic nominating contest that year to Barack Obama and then to become Obama’s secretary of state in 2009.

“She's got dyed blonde hair and pouty lips, and a steely blue stare, like a sadistic nurse in a mental hospital,” Johnson wrote then.

Despite his strong dislike for what he called “an all-round purse-lipped political correctness,” Johnson endorsed Clinton in that column. But he sounds a bit more reluctant to weigh in this time around.

“She’s an extraordinary politician,” Johnson told the Evening Standard this week. “But I think it would be wrong of me to intrude on election campaigns in America and indeed I wouldn’t want to blight any candidate with my endorsement.

“I should also stress I have met Republican potential candidates and think very highly of them,” he added.

There has been a parade of U.S. politicians in London recently – including Wisconsin Gov. Scott Walker, who is currently in England – and Johnson has met several of them, including former Florida Gov. Jeb Bush and New Jersey Gov. Chris Christie. Those visits are seen as attempts to raise the stature of U.S. politicians -- not unlike Johnson’s visit here, aimed as showcasing him as a rising player on the global stage.

Johnson did not, however, have kind words for Louisiana Gov. Bobby Jindal, who recently caused a stir when he gave a speech in London and suggested Muslims in Britain had created “no-go” areas where non-Muslims were not welcome.

Johnson said Jindal needed “urgent and gentle” re-education. "I invite him to come and see London in its totality, every area of the city and see that there are absolutely no no-go.”

Johnson, who was born in New York and holds dual citizenship, had to take care of a bit of business before his visit: last month, he settled an unspecified – but large – U.S. tax bill that he had earlier complained was outrageous, since he had not lived in the United States since he was 5 years old.

“Yes, I was born in New York. What a very expensive decision that turned out to be,” Johnson joked Wednesday as he touted tech investment in the United Kingdom and partnership with American financial and other businesses.

Introducing Johnson at that event, Huffington Post editor Ariana Huffington suggested that as a dual citizen, Johnson’s ambitions may go beyond No. 10.

“We have a lot to share, including my hope that one day, given that he has dual citizenship, he may visit New Hampshire and Iowa and run for president,” Huffington joked.

After Clinton does, presumably.

Mary Jordan contributed to this report.