War and politics were colliding for Lyndon Johnson in March 1968 as he talked tough to a foreign enemy while assuring key backers – people he badly needed for his re-election campaign – that he yearned for peace, tapes released Thursday show.

The embattled president faced a commander of U.S. forces in Vietnam who wanted more troops, a Congress that wouldn't pass his tax bill to pay for the war and political embarrassment after an obscure Minnesota senator almost beat him in the New Hampshire primary.

"I don't think we can run this war like we’re running it," Mr. Johnson told Secretary of State Dean Rusk in early March 1968, as the two men discussed sending 20,000 more soldiers to the war in Southeast Asia.

"I just don’t think we can keep on delaying and wait until a fatal day and find out we were too little, too late," the Democratic president said.