WASHINGTON — President Trump said on Monday that he would not apologize for campaign statements calling for a “Muslim ban,” appearing to undercut an assertion at a Supreme Court argument last week from Solicitor General Noel J. Francisco. In defending Mr. Trump’s efforts to restrict travel from several predominantly Muslim countries, Mr. Francisco said that the president had already disavowed the statements.

Mr. Francisco’s own assertion contained a mistake, a Justice Department spokeswoman said on Monday. “The president has made crystal clear on Sept. 25 that he had no intention of imposing the Muslim ban,” Mr. Francisco said during the argument. But he got the date wrong by eight months, and critics said the statement he referred to was less than crystal clear.

Mr. Trump’s comment and the Justice Department’s clarification arose from an exchange at Wednesday’s argument.

Chief Justice John G. Roberts Jr. asked whether Mr. Trump could immunize his order from constitutional challenge by disavowing his campaign statements.