For the first 12 days, the Obama administration’s effort to extradite government leaker Edward Snowden from Hong Kong was a by-the-book legal affair — overseen by the Justice Department and involving few if any diplomatic overtures, according to senior administration officials.

That legalistic approach has resulted in a political and public relations debacle. By the time U.S. officials had begun applying diplomatic pressure on Hong Kong and Chinese authorities last weekend, it was too late: Snowden had boarded a flight to Moscow in search of asylum.

The missteps have thrust the United States into a geopolitical confrontation that has embarrassed the Obama administration and strained relations with China, Russia and other countries.

President Obama on Thursday defended the handling of the international chase for the former government contractor, calling it a legal matter and saying he was “not going to be scrambling jets to get a 29-year-old hacker.” Asked whether he had personally called Chinese President Xi Jinping or Russian President Vladi­mir Putin about Snowden, Obama said he had not.

“I shouldn’t have to,” Obama added at a news conference in Senegal. “I’m not going to have one case of a suspect who we’re trying to extradite suddenly being elevated to the point where I’ve got to start doing wheeling and dealing and trading on a whole host of other issues simply to get a guy extradited.”

The scramble to catch Snowden

But many experts in extradition law argue that that is precisely what’s needed in the case. They said the Obama administration underestimated how much diplomatic finesse and creativity would be required to detain Snowden, allowing him to move further outside the reach of the U.S. government.

“The administration followed the playbook and played it correctly, except what they didn’t seem to anticipate is that Hong Kong would not comply,” said Jacques Semmelman, a former federal prosecutor and expert on extradition procedure.

Stephen I. Vladeck, an associate dean at American University’s Washington College of Law who studies national security law, said the administration made mistakes by just going “through the motions.”

“It should have been clear from the get-go that the government was going to need more than just a prima facie case for extradition here, but also the political and diplomatic cooperation of the Hong Kong — and, perhaps, Chinese — authorities,” Vladeck said.

P.J. Crowley, a former State Department spokesman under Secretary of State Hillary Rodham Clinton, said extradition requests as high-profile as Snowden’s should not be seen “through a legal lens.”

“This is about politics and about perceived and competing interests on all sides,” Crowley said. He added: “When it becomes public, then it becomes a diplomatic issue. And when it becomes personal, it becomes a political issue.”

To be sure, the full extent of the Obama administration’s diplomatic entreaties to Hong Kong and Beijing might not be known publicly. Considering the profile of Snowden’s case, experts said they would be surprised if there had not been secret high-level diplomatic talks between U.S. officials and authorities in Hong Kong and Beijing.

“They don’t like to make this public,” said Leslie H. Gelb, president emeritus of the Council on Foreign Relations. “They’d rather do it by the books, because if China and Russia reject us, it’s better to reject the Justice Department than the White House.”

Still, the Obama administration’s public accounts thus far show that it pursued Snowden’s extradition from Hong Kong primarily through legal channels. When Obama was asked about Snowden on Monday, he referred reporters to the Justice Department.

After Snowden revealed himself June 9 as the leaker of classified documents revealing National Security Agency surveillance programs, administration officials said they followed interagency protocols in trying to return Snowden to the United States to stand trial.

The White House’s National Security Council has coordinated the broad response to the Snowden case but let officials at the Justice Department — lawyers, not diplomats — take the lead on the extradition process and make their own decisions, according to a senior administration official. The official, like others interviewed, spoke on the condition of anonymity to discuss details of the government’s response.

Although the Justice Department followed protocol laid out in its extradition treaty with Hong Kong, there were also some low-level communications between U.S. consulate officials and the Hong Kong and Chinese governments, administration officials said.

On June 14, the United States filed criminal charges against Snowden in federal court, but they took a gamble by sealing the charges — which meant they could not use them as cause to revoke his passport. U.S. officials said they feared Snowden might flee if he found out about the charges, and they wanted time to work out the provisional arrest request with Hong Kong.

Extradition is generally a lengthy process, but Justice Department officials believed it was advancing at a rapid pace with Snowden. “It was an unbelievably quick turnaround,” one law enforcement official said.

On June 19, Attorney General Eric H. Holder Jr. called his counterpart in Hong Kong, Secretary for Justice Rimsky Yuen, to personally underscore the importance of arresting Snowden. At the White House, where national security aides kept Obama up to speed with regular briefings, officials said they believed Justice lawyers were close to an agreement.

But on the night of June 21 — after the Justice Department had unsealed Snowden’s criminal charges — U.S. officials realized they had hit a snag, according to a senior administration official. That’s when Hong Kong authorities raised questions about the U.S. charges against Snowden and sought clarification about paperwork, the official said.

As U.S. officials were preparing a response letter and fired off their first strongly worded public statement warning Hong Kong of complicating relations with the United States, they learned that Snowden was on an Aeroflot flight bound for Moscow, the senior administration official said.

“It wasn’t necessarily clear that someone other than the Department of Justice and the interagency process we already had was going to be needed,” the official said.

In the final hours before Snowden departed, the State Department stepped up its involvement. On Saturday, State revoked his passport, according to a senior State Department official. A passport cannot be revoked in a criminal matter until the charges are made public, which had just been done the night before, the official said.

Hong Kong authorities said they did not receive the official U.S. notice until Wednesday. But State Department spokesman Patrick Ventrell said they “were well aware of our interest in Mr. Snowden and had plenty of time to prohibit his travel.”

Yuen, the Hong Kong justice minister, said this week that his country allowed Snowden to travel because of alleged mistakes by the United States in making the extradition request. Yuen said in an interview with the South China Morning Post that the name used in U.S. diplomatic documents was Edward James Snowden, while the Justice Department referred to him as Edward J. Snowden and Hong Kong’s Immigration Department had him recorded as Edward Joseph Snowden.

Yuen also said the United States failed to provide adequate evidence or explain how two of the three charges in its arrest request fell within the scope of the extradition treaty signed by both nations in 1996.

U.S. officials insisted that they followed procedure and said Hong Kong’s concerns amounted to a stalling tactic. One U.S. official close to the discussions said Hong Kong’s claim that it could not properly identify Snowden because of inconsistencies in his middle name was “laughable,” noting that his videotaped confession was being replayed “all over the news.”

Justice officials said that if Hong Kong authorities really wanted the issue clarified, they would have waited for U.S. officials to provide answers before allowing Snowden to leave the country.

Experts said that Hong Kong authorities seized on procedural irregularities, fairly or not, to delay the U.S. request long enough to allow Snowden to flee to Russia.

“It’s really hard to play Monday-morning quarterback in a case like this,” Vladeck said, “because there’s no guarantee that Hong Kong would have cooperated — even if all the i’s had been dotted and t’s crossed.”

As for Snowden, all evidence suggests he remains ensconced in the transit area at Moscow’s Sheremetyevo Airport. On Thursday, another daily Aeroflot flight to Havana closed its doors without any sign that the American fugitive was on board.

Anne Gearan in Washington, Kathy Lally in Moscow, David Nakamura in Dakar, Senegal, and Jia Lynn Yang in Hong Kong contributed to this report.