People close to the president believe that he may be increasing his legal jeopardy by continuing to speak publicly about sensitive matters even as his campaign is under investigation for possible collusion with Russia and he himself is under scrutiny for possible obstruction of justice. Just last week, Mr. Trump said in a tweet that Attorney General Jeff Sessions should shut down the special counsel investigation.

While the president tried again on Sunday to portray the Trump Tower meeting as routine, it is being examined as part of Mr. Mueller’s investigation into whether Mr. Trump’s campaign conspired with the Russians to undermine Hillary Clinton’s campaign.

It is illegal for a campaign to accept help from a foreign individual or government. The president and his son have maintained that the campaign did not ultimately receive any damaging materials about Mrs. Clinton as a result of the meeting. But some legal experts contend that by simply sitting for the meeting, Donald Trump Jr. broke the law.

In his tweet on Sunday, the president denied a report in The Washington Post that he was worried about the legal exposure for Donald Trump Jr. While the president said that the meeting was legal, he also distanced himself from it, repeating his assertion that he knew nothing about it at the time.