FILE - In this May 3, 2017 file photo, White House senior adviser Jared Kushner is seen at the White House in Washington. (AP Photo/Evan Vucci, File)

FILE - In this May 3, 2017 file photo, White House senior adviser Jared Kushner is seen at the White House in Washington. (AP Photo/Evan Vucci, File)

WASHINGTON (AP) — Smart diplomacy or inappropriate and possibly illegal?

Jared Kushner’s reported attempt to establish a “back-channel” line of communication between Russia and Donald Trump’s presidential transition team is proving divisive, even if such talks aren’t unusual.

Supporters of the president say it’s laudable that Kushner, Trump’s son-in-law and a trusted adviser, was working even before the inauguration to foster better relations with Russia.

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Critics say it’s a matter of context and timing. They call it a giant and arrogant step over the line — perhaps even treasonous — for a private citizen to try to set up covert communications with a hostile power like Russia, particularly after U.S. intelligence agencies accused Moscow of trying to interfere in the 2016 election to help Trump.

A look at what constitutes back-channel diplomacy, some examples from history and the risks and benefits of such informal communications.

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DEFINITION, PLEASE

Back-channel diplomacy refers to unofficial but direct, high-level communications that bypass formal channels, according to “Safire’s Political Dictionary.” These talks sometimes can help governments work through difficult problems and reduce tensions in lower-pressure settings away from the limelight. “They can be an incredibly effective tool in the diplomatic tool box,” says Richard Moss, a professor at the U.S. Naval War College and author of the book, “Nixon’s Back Channel to Moscow: Confidential Diplomacy and Detente.” But Moss added that such channels “work best when they supplement rather than supplant traditional diplomacy.”

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A COMMON PRACTICE

Back-channel talks have been common in U.S. diplomacy, especially when Washington lacks formal ties with another government it wants to speak with.

The Obama administration, for example, approved months of secret meetings between U.S. and Iranian officials to clinch an interim 2013 nuclear deal.

When the deal was done, President Barack Obama said the early informal talks explored “how much room” existed to get something done. Once the work became more technical, they merged into public talks with world powers.

U.S. back-channel diplomacy with Cuba has its own long history. It spans the secret talks leading to Obama’s 2014 agreement to re-establish diplomatic ties to the 1962 Cuban missile crisis, when President John Kennedy used his brother, Attorney General Robert Kennedy, to help defuse the crisis. President Richard Nixon used multiple back channels to interact with the Soviet Union.

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TRANSITION PERIODS

Back-channel talks during a presidential transition period can be particularly sensitive, as an incoming administration looks to get a head start on diplomacy while the current president still holds power. That’s one reason the Kushner overtures are getting so much attention. But even transition back channels aren’t unprecedented.

Nixon set up two back channels to the Soviets while waiting to take over from President Lyndon Johnson, Moss says, including talks between Nixon political adviser Henry Kissinger and KGB operative Boris Sedov.

Those talks proved to be a “fruitful back channel between the leadership of our two countries,” former KGB general Oleg Kalugin wrote in “Spymaster: My Thirty-two years in Intelligence and Espionage Against the West,” adding that Kissinger “began to convey to us that Nixon was no anti-Communist ogre and that he wanted improved relations with USSR.”

Moss said longtime Nixon aide Robert Ellsworth also had a back channel with the Soviet ambassador and another Soviet diplomat that Nixon used, among other things, to kill Johnson’s idea of a summit involving his outgoing administration, the incoming Nixon team and the Kremlin.

There have been persistent allegations of back-channel talks between aides close to Republican presidential candidate Ronald Reagan and the Iranian government in 1980 amid U.S. negotiations to release American hostages in Iran. Reagan always denied such parallel talks. The hostages were freed hours after Reagan’s 1981 inauguration.

Obama wasn’t averse to informal diplomatic channels before his 2008 election. When foreign policy adviser Daniel Kurtzer met with Syrian President Bashar Assad’s foreign minister in the summer of 2008, Obama’s campaign stressed that Kurtzer wasn’t a paid adviser or authorized to conduct talks with any government. Still, Obama’s Republican rival, Sen. John McCain of Arizona, criticized the outreach. McCain is now among those raising concerns about Kushner’s proposed back-channel talks.

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KUSHNER’S CONTACTS

What exactly was Kushner up to? He talked to Russian Ambassador Sergey Kislyak about opening up a line of communication to explore options as the new administration developed a Syria policy, according to a person familiar with the discussions. The intent was to connect Trump’s chief national security adviser at the time, Michael Flynn, with Russian military leaders. In Syria’s civil war, Russia has backed Assad. The U.S. has supported anti-Assad rebels. Kushner proposed using Russian diplomatic facilities for the discussions, apparently to make them more difficult to monitor, according to The Washington Post. Flynn never ended up using Russian facilities to talk to Moscow, U.S. officials said.

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CONTEXT IS EVERYTHING

Kushner’s outreach, at a time of alleged Russian meddling in the U.S. election, has fed accusations of Trump campaign collusion, which the FBI is investigating.

Eliot Cohen, a veteran of George W. Bush’s State Department, tweeted that contacts between a transition team and foreign diplomats are normal. “What is not normal,” he added, “is asking a hostile government to provide secure comms to avoid FBI/NSA surveillance.”

Former CIA boss Michael Hayden asked on CNN: “What manner of ignorance, chaos, hubris, suspicion, contempt would you have to have to think that doing this with the Russian ambassador was a good or an appropriate idea?”

Back channels are fine, Hayden said, “but you don’t do it when you’re not the government and I don’t think you do it using your adversary’s communications system.”

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IS IT LEGAL?

Kushner’s contacts have revived talk about the Logan Act, a centuries-old law that prohibits U.S. citizens from trying to influence a foreign government in disputes with the United States. The act has been used so rarely that legal experts say it may no longer be valid. And no one has ever been found guilty of violating it.

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Follow Nancy Benac on Twitter at http://twitter.com/nbenac