Republican John McCain argued on Thursday that presidential rivals Rudy Giuliani and Mitt Romney lack the foreign policy experience to make the inevitable tough decisions of a wartime commander in chief.

"We have to make far-reaching reforms to our government to prepare for the long threat our enemies plan for us, and the cruel and desperate means they will employ to harm us," McCain said in a speech to the conservative Hudson Institute. "You don't just talk about or manage such changes, you lead them."

The four-term Arizona senator and Vietnam veteran argued that the next president needs "tested experience, political courage and strategic clarity to make sound and difficult decisions" -- implying he embodies all three attributes.

"Tough talk or managerial successes in the private sector aren't adequate assurance that their authors have the experience or qualities necessary for such a singular responsibility," McCain said, a clear reference to his two top competitors.

Giuliani is a former two-term mayor of New York who moved into the business sector after elective office. Romney is a venture capitalist and one-term former governor of Massachusetts. Like another leading candidate, Fred Thompson, their campaign speeches are filled with sharp rhetoric about defeating terrorists although their foreign policy resumes are thin compared with McCain's.

He also called for increasing the number of soldiers and Marines from the planned level of about 750,000 to 900,000 without reinstituting the draft.

McCain delivered his speech as his campaign rolled out the first television and radio ads in the early primary state of New Hampshire, which is emerging as a must-win state for the former GOP front-runner whose fortunes plunged this summer. He's seeking a comeback, and, in the ads, emphasizes his war-hero biography and decades-long experience on military matters.

In the speech, McCain painted an optimistic picture of military progress in Iraq but he also warned of a long slog ahead. He distanced himself from President Bush on military issues, saying: "We are in a long war, a war I am afraid the U.S. government is not adequately prepared to fight."

Without naming Democrats Hillary Rodham Clinton, Barack Obama or John Edwards, McCain accused his rivals of political cowardice and said: "They offer nothing other than generalities based on a withdrawal that amounts to defeat."