By Jim Sciutto, Michael Rios, CNN

(CNN) — The US special forces veteran whose rescue team spirited Nobel laureate María Corina Machado out of Venezuela has begged her not to return to the country, after a perilous extraction mission that lasted nearly 16 hours and was carried out largely in the middle of the night through rough waters.

“Overwhelmingly, this is the hardest, most high profile, most delicate operation we’ve conducted,” Grey Bull Rescue Foundation founder Bryan Stern told CNN on Friday.

Stern told a virtual press conference earlier that Machado had boarded a boat that set sail from the Venezuelan coast to a rendezvous point at sea. That’s where she met Stern, who was waiting for her on another boat.

She reached and boarded the second vessel by Tuesday night and was ferried to a different location.

The nighttime journey at sea was long, cold and full of tension, and was made even more challenging because of her high profile.

“Because of her face, because of her signature, because the entire Venezuelan intelligence service, the entire Cuban intelligence service, parts of the Russian intelligence, were all looking for her for months, and specifically this week, in particular, because of the Nobel Prize, (it) made this operation significantly more high risk than we’ve ever done before,” he said.

He told CNN that his team has carried out 800 operations and rescued more than 8,000 people, but this was “the first person that has a Wikipedia page.”

Stern previously told reporters that the boat reached the shore early Wednesday morning. From there, Machado boarded a plane bound for Norway, where she was due to accept her Nobel Peace Prize and see her daughter for the first time in two years.

According to flight tracking data verified by CNN, the plane Machado used to arrive in Oslo took off Wednesday morning from Curaçao, an island near Venezuela, and stopped in Bangor, Maine, before heading to Norway. The Dutch Embassy in Caracas, which is responsible for representing the interests of Aruba, Bonaire and Curaçao, has denied any involvement in Machado’s escape.

Machado arrived in Oslo just hours after the ceremony for the Nobel Peace Prize, which her daughter accepted on her behalf. She was greeted by crowds of cheering supporters who she waved to from the balcony of Oslo’s Grand Hotel, and later said she met many Venezuelans hopeful they might one day return to a liberated country.

It was Machado’s first public appearance in almost a year. She went into hiding after the Venezuelan government moved to crush dissent following last year’s disputed election, resurfacing only briefly at a protest in January against the swearing-in of President Nicolás Maduro.

Machado’s team on Friday declined to comment on the extraction operation and didn’t confirm to CNN whether the Grey Bull rescue team was involved.

Machado previously told reporters that she received support from the US government but declined to provide details, saying, “One day I will be able to tell you, because certainly I don’t want to put them in risk right now.”

Stern has said the operation was funded by anonymous donors and – to his knowledge – was not supported by the US government.

But at a virtual press conference earlier on Friday, he acknowledged that his team did communicate with the US military to make them aware of their presence at sea. He said he wanted to avoid being targeted in the ongoing US operation against alleged drug boats in the Caribbean.

“In this case, because the US military is conducting operations in this part of the world, I was worried about – I was deeply concerned about being targeted by the US military,” he told reporters.

“We communicated in such a way where the US government, the US military, knew that we were doing something in the region. They did not know the details of it. They knew where we would be operating, where some of our rally points were, and then at the very highest levels and the very last minutes we disclosed what the objective was,” he added.

Asked if his team would ever help Machado return to Venezuela, Stern said he advised her against it.

“When we were on the boat together, we talked about this, and I begged her not to go back,” he told CNN. “She’s a real hero and icon of mine, and to put her back in harm’s way where she may be arrested, killed, tortured, who knows what? – I would really not want to do that, but like us, she’s a leader, and she wants to be there for her people.”