New York ? Vice President Dick Cheney ridiculed John Kerry on Wednesday night as a wishy-washy presidential pretender whose election would jeopardize America’s security.

“History has shown that a strong and purposeful America is vital to preserving freedom and keeping us safe,” Cheney told the GOP national convention in a blistering assault on the Democratic nominee. “Yet time and again, Sen. Kerry has made the wrong call on national security.

“On Iraq, Senator Kerry has disagreed with many of his fellow Democrats, but Senator Kerry’s liveliest disagreement is with himself,” Cheney added to thunderous laughter from the delegates. “His back-and-forth reflects a habit of indecision, and sends a message of confusion. And it is all part of a pattern.”

Warming to the Bush campaign’s theme that Kerry is a pathological flip-flopper, Cheney offered a litany of issues on which Kerry has changed his mind, then mockingly noted: “Senator Kerry says he sees two Americas. It makes the whole thing mutual — America sees two John Kerrys.”

Several of Cheney’s attack lines were staples of his stock stump speech, but they took on added impact before a prime-time television audience numbering millions more than the veep has reached in his dozens of campaign appearances this year.

Time and again, Cheney portrayed Kerry as not merely a weak opponent but a dangerous one.

“In his years in Washington, John Kerry has been one of a hundred votes in the United States Senate — and very fortunately, on matters of national security, his views rarely prevailed. But the presidency is an entirely different proposition.

“A senator can be wrong for 20 years (but) in this time of challenge, America needs — and America has — a president we can count on to get it right.”

Warming to the task described by one senior Bush aide as “a character witness for the president,” Cheney praised his boss as “a man of great personal strength — and more than that, a man with a heart for the weak, and the vulnerable, and the afflicted.”

Cheney said Bush’s re-election is essential because this election comes at a crossroads in history “when leaders must make fundamental decisions about how to confront a long-term challenge abroad and how to keep the American people secure. This nation has reached another of those defining moments.

“On the question of America’s role in the world, the differences between Sen. Kerry and President Bush are the sharpest, and the stakes for the country are the highest,” Cheney argued.

Before Cheney spoke, Georgia Sen. Zell Miller, the keynote speaker, delivered a blistering denunciation of fellow Democrat Kerry, charging he has voted repeatedly to hamstring the American military.

Listing weapons programs Kerry has voted against, Miller asked: “This is the man who wants to be the commander in chief of our U.S. armed force? … Armed with what? Spitballs?”