Donald Trump has wished his "enemies" a Happy New Year in a barbed tweet posted just weeks before he takes office in the White House.
In the gloating New Year's Eve message, the President-elect wrote: "Happy New Year to all, including to my many enemies.
"Those who have fought me and lost so badly they just don't know what to do. Love!"
Earlier Trump praised Putin for holding off on plans to expel US diplomats from Russia in a tit-for-tat retaliation against Washington.
He said the Russian President's decision to delay any expulsion of American officials was a "great move", and tweeted: "I always knew he was very smart!"
Great move on delay (by V. Putin) - I always knew he was very smart!
— Donald J. Trump (@realDonaldTrump) December 30, 2016
On Thursday, President Barack Obama ordered 35 suspected Russian spies to leave America, and imposed sanctions on two Russian intelligence agencies over their involvement in hacking political groups prior to November's election.
Russia was expected to retaliate by expelling 35 US officials from Moscow and St Petersburg.
But in a surprise announcement, Mr Putin said he would not "create problems for American diplomats" and invited their children to visit the Kremlin instead.
Mr Putin has said he reserves the right to retaliate in future, but will wait and see how Donald Trump acts following his inauguration in less than three weeks' time.
The President-elect's complimentary tweet to Mr Putin, when combined with the cabinet nominations of some people seen as friendly towards Russia, has the potential to anger Republicans who have been calling for a tougher stance against the one-time Cold War foe.
On Thursday, Mr Trump appeared to brush aside allegations from US intelligence agencies that Russia was behind a series of cyber attacks, saying: "It's time for our country to move on to bigger and better things."
It's also possible that the new president could reverse Mr Obama's decision to expel the Russian diplomats once he enters office on 20 January.
The diplomats affected by the expulsion are based in Washington and San Francisco, and include a consulate chef.
The US also plans to shut Russian compounds in New York and Maryland, with the FBI publishing "wanted" posters of alleged Russian hackers.
Yesterday, the Washington Post reported that Russian hackers had successfully penetrated an electric utility in Vermont but did not disrupt its operations - a development which would suggest a serious vulnerability in the nation's electrical grid.
Mr Putin said the latest sanctions were a "provocation aimed to further undermine Russian-American relations" and that he regretted that Mr Obama's administration would end in this way.
The Russian embassy in the UK tweeted that "everybody, incl (the American) people, will be glad to see the last of this hapless Adm", together with a picture of a "lame duck".
But The Kremlin has said that, with Mr Obama only in office for three more weeks, it will refrain from acting like a "bull in a china shop".
In a statement announcing the measures, President Obama said they were a "necessary and appropriate response" after repeated warnings to Russia over "efforts to harm US interests".
He said the alleged hacking "could only have been directed by the highest levels of the Russian government", adding: "All Americans should be alarmed by Russia's actions."
