People in Sweden have been scratching their heads since Mr Trump suggested during a rally Friday that some sort of incident had occurred in their country.
No incident occurred in Sweden and the country's government has asked the US State Department to explain.
Mr Trump tweeted on Sunday he was referring to something he saw on television.
The president might be referring to a segment aired on Friday night on the Fox News Channel show Tucker Carlson Tonight that reported Sweden had accepted more than 160,000 asylum-seekers last year but that only 500 of the migrants had found jobs in Sweden. The report went on to say that a surge in violence had followed.
RUSSIAN 'COMPILING TRUMP DOSSIER FOR PUTIN'
Russian officials are reportedly compiling a psychological dossier on Mr Trump for Russian President Vladimir Putin ahead of their first meeting.
Among the conclusions is that Mr Trump is a naive risk-taker who "doesn't understand fully who is Mr Putin - he is a tough guy".
Former Deputy Foreign Minister Andrei Fedorov told NBC News that the file is being put together by retired diplomats and some of Mr Putin's staff to help the Russian leader plan for his first meeting with the Republican billionaire. The meeting date has not yet been decided.
"Very serious preparatory work is going on in the Kremlin, including a paper - seven pages - describing a psychological portrait of Trump, especially based on this last two to three months, and the last weeks," added Mr Fedorov, who said he has known Mr Trump since 2000.
He also said the dossier was being revised regularly, adding that many in the Kremlin believe Mr Trump sees the presidency as a business.
"Trump is not living in a box - he is living in a crowd. He should listen to the people around him especially in the areas where he is weak," Mr Federov said. "Trump cannot come to a meeting with Putin as a loser - he must sort out his domestic problems first."
NBC News reports it is normal for leaders to be fully briefed on who they are meeting, detailed dossiers "on the mind and instincts of a US leader is unusual".
Mr Fedorov said Mr Putin's government is growing increasingly concerned about Mr Trump's ongoing controversies in Washington. They also fear he does not have the political power to improve relations with Russia, as he has promised.
It comes after US intelligence agencies concluded that Russia worked to undermine the US election process in a bid to help Mr Trump win the White House.
MATTIS: 'US NOT IN IRAQ TO SEIZE OIL'
In a bid to soothe partners rattled by Mr Trump, Defence Secretary Jim Mattis told reporters in Baghdad that the United States is not about to plunder Iraq's petroleum reserves.
Mr Trump has repeatedly said both while campaigning and since his election that America, whose troops occupied Iraq for eight years, should have grabbed Iraqi oil to help fund its war effort and to deprive the Islamic State group of a vital revenue source.
But Mattis, a retired Marine general who commanded troops during the 2003 invasion of Iraq, appeared to nix the idea on Monday.
"All of us in America have generally paid for gas and oil all along, and I am sure that we will continue to do so in the future," Mattis said at the start of a visit to Iraq. "We are not in Iraq to seize anybody's oil."
PENCE: TRUMP EXPECTS 'REAL PROGRESS' ON NATO
Mr Trump expects NATO allies to make real progress by the end of this year towards the increased defence spending target agreed by the alliance, his Vice President Mike Pence said on Monday.
"The president of the United States and the American people expect our allies to keep their word and to do more in our common defence ... the president expects real progress by the end of 2017," Mr Pence said after talks with NATO head Jens Stoltenberg in Brussels.
UK POLITICIANS TO DEBATE TRUMP VISIT
British lawmakers are set to debate a call for Mr Trump to be denied a state visit to the UK - but the Conservative government insists the invitation remains firmly in place.
Trump opponents plan to demonstrate outside Parliament in London as legislators hold a non-binding debate on Monday.
It comes in response to an online petition with more than 1.8 million signatures saying a formal state visit "would cause embarrassment to Her Majesty the Queen."
On state visits, foreign leaders are welcomed with royal pomp and military ceremony, and usually stay at Buckingham Palace as guests of Queen Elizabeth II.
Lawmakers will also consider an opposing petition, with more than 300,000 signatures, backing the state visit.
