"I do not believe, not have I ever stated, publicly or privately that Israel is an apartheid state or that it intends to become one," the top US diplomat said in a strong statement after calls for him to resign or at least apologize for the alleged comments.
"Anyone who knows anything about me knows that without a shred of doubt."
But Kerry, who has seen his dogged efforts to broker peace between Israel and the Palestinians collapse, did suggest that he had used a poor choice of words during his speech Friday to international experts of the Trilateral Commission.
The Daily Beast online news site reported that Kerry had warned that "a unitary state winds up either being an apartheid state with second-class citizens - or it ends up being a state that destroys the capacity of Israel to be a Jewish state."
More From This Section
Kerry has "repeatedly demonstrated a willingness to countenance a world in which Israel is made a pariah," said Senator Ted Cruz.
"Before any more harm is done to our national security interests and our critical alliance with the state of Israel," Kerry should offer his resignation and President Barack Obama should "accept it," he added.
Veteran Republican Senator John McCain also said Kerry should clarify his comments immediately and apologize, but laughed at the suggestion the top US diplomat should step down.