'Great move'

President-elect Donald Trump on praised President Vladimir Putin for refraining from tit-for-tat expulsions of Americans in response to US punitive measures over alleged Russian interference in the November election.

Putin's decision came despite the foreign ministry asking him to send home 35 US diplomats after President Barack Obama had expelled the same number of Russian staff.

Trump's intervention -- in a tweet -- however illustrated the shifting political tide in Washington, barely three weeks before the Republican is due to succeed Obama at the White House.

"Great move on delay (by V. Putin) - I always knew he was very smart!" the incoming US president wrote.

Russia's embassy in Washington quickly retweeted the comment, which Trump pinned so it would appear at the top of his feed for several hours.

Trump's tweet enraged his Democratic foes as well as some members of his own Republican Party.

Claire McCaskill, a Democrat who serves on the Senate Armed Services Committee, wrote: "Our ENTIRE cyber intel community, best in world btw, agrees that this guy tried to mess in our election & the Russians are RT TrumpPutin love."

The alleged hacking of the US presidential election in November outraged Obama, culminating in the expulsions and other sanctions.

But outlining why he would not retaliate, Putin cited Trump's imminent accession.

"We will not expel anyone," Putin said in a statement, also inviting children of US diplomats to a holiday party at the Kremlin.Instead, Moscow will plan its next steps "based on the policies pursued by the administration of president Donald Trump," while warning that the Kremlin reserves the right to respond.

The Russian leader chided the outgoing Obama for "unfriendly steps" amounting to "a provocation aimed at further undermining Russian-American relations."

Obama on Thursday unleashed a barrage of sanctions against Russia over alleged cyberattacks aimed at tilting the November election in Trump's favour.

The move follows years of bad blood with Putin that had seen Washington slap sanctions on Moscow over its behavior in Ukraine and Syria.

US intelligence has concluded that the Kremlin ordered a hack-and-release of Democratic Party and Hillary Clinton campaign staff emails in a bid to put Trump in the Oval Office.

Moscow has repeatedly denied the hacking allegations.