WASHINGTON — President Trump on Wednesday called a Turkish incursion into Syria “a bad idea” but reiterated his opposition to “endless, senseless wars,” striking a far milder tone than outraged members of Congress, foreign allies and officials in his own administration, who said the offensive must be stopped.

And later in the day, after issuing that statement, Mr. Trump seemed dismissive of the plight of the Syrian Kurdish fighters who are in Turkey’s cross hairs.

Speaking to reporters, the president said that while the Kurds had fought alongside American troops against the Islamic State, or ISIS, they had done so out of self-interest, “for their land,” and noted that “they didn’t help us in the Second World War. They didn’t help us with Normandy.”

“With all that being said, we like the Kurds,” he added.

In his earlier statement, Mr. Trump said he was holding Turkey responsible for preventing the release of Islamic State fighters who were being held captive in the area and for ensuring “that ISIS does not reconstitute in any way, shape or form.”