White House spokesman Sean Spicer repeated allegations that a Democratic operative had met with Ukrainian embassy officials during the campaign.
Spicer referred to several recent reports by conservative media outlets, alleging the Democratic operative sought dirt on then Trump campaign director Paul Manafort.
The allegations first came to light in a Politico story in January.
"Obviously, there's been a lot more interest in recent days with respect to what the DNC did in coordination with the Ukrainian government to try to collude," Spicer said.
The White House spokesman alleged that the Democratic National Committee collusion took place to "achieve a goal of having someone removed, which ultimately did happen."
Manafort left his post in August 2016, as Trump's general election prospects looked dim and details of his own business dealings with pro-Kremlin leaders in Ukraine emerged.
Spicer was asked by a pro-Trump media representative whether the issue was raised when Ukrainian President Petro Poroshenko visited the White House in June.
Spicer said he did not know, but claimed that "the DNC's collusion with the Ukrainian government has definitely gotten a lot more attention since that meeting."
Adrienne Watson of the DNC accused the White House of deflecting.
"The White House has been pushing this narrative to distract from the Trump campaign's willingness to work with a hostile foreign government to interfere in our election. No one is buying it."
The comments come as the White House reeled from Donald Trump Jr's confession that he and two other Trump senior aides knowingly met Kremlin-connected operatives to get incriminating information on rival presidential candidate Hillary Clinton.
US intelligence agencies believe that President Vladimir Putin ordered a vast influence operation to tilt the 2016 election in Trump's favor.
Trump himself has responded by describing his son's meeting as business as usual.
"Most politicians would have gone to a meeting like the one Don jr attended in order to get info on an opponent. That's politics!" he tweeted on Monday.
Spicer seemed to contradict his boss, by saying the meeting was actually about adoption.
In a statement, the Ukrainian embassy in Washington denied allegations it had "colluded" with Democrats against the Trump campaign.
The embassy "neither coordinated with the DNC on opposition research nor taken any actions to undermine campaign efforts," the statement read.
"While some politicians who are not part of the Ukrainian government might have taken sides or made comments during last year's election, the Embassy and the government of Ukraine did not."
"We highly appreciate US administration support to Ukraine and the progress achieved in recent months in our bilateral relations."
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