A Russian military intelligence unit linked to assassination attempts in Europe had offered rewards for successful attacks last year.
Russia says Whelan was caught red-handed with a computer flash drive containing classified information.
Russia informed the US embassy that Whelan had undergone the surgery on Thursday.
Whelan, a US national who also holds British, Canadian and Irish passports, has been in custody since he was detained in a Moscow hotel room in December 2018.
Barr launched a review earlier this year to investigate Trump's complaints that his campaign was improperly targeted by U.S. intelligence and law enforcement agencies during the 2016 election.
The treaty bans either side from stationing short- and intermediate-range, land-based missiles in Europe.
Kushner, a top aide to Trump, is among 12 subpoenas approved Thursday in a party-line vote.
Pompeo will hold talks with European officials on Iran and other issues on Monday before heading to Russia.
After two years of major unilateral decisions, the White House faces numerous crises that it has kindled in the hope that at least one will turn out in its favor.
The United States is now set to start the six-month process of quitting from the 1987 Intermediate-range Nuclear Forces Treaty.
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