Washington: Republican vice presidential candidate Sarah Palin said on Thursday if Georgia was admitted to Nato, the United States would be obliged to defend the former Soviet republic against an attack from Russia.

Palin, the relatively unknown governor of Alaska chosen two weeks ago to be John McCain's running mate in the White House race, said she was up to the challenge of being the country's No. 2 official.

In her first media interview, Palin was asked by ABC News if the United States would be bound to go to war if Russia invaded Georgia again.

"Perhaps so. I mean, that is the agreement when you are a Nato ally, is if another country is attacked, you're going to be expected to be called upon and help," she told interviewer Charles Gibson.

"And we've got to keep an eye on Russia. For Russia to have exerted such pressure in terms of invading a smaller democratic country, unprovoked, is unacceptable," she said.

Palin, a conservative anti-abortion and pro-gun rights mother of five, has fired up Republican Party grassroots activists and ignited a surge of momentum for McCain in the race against Obama.

Opinion polls showed McCain and Palin running even or slightly ahead of Obama and his running mate, Delaware Sen. Joe Biden, after last week's Republican convention. Obama, an Illinois senator, held a slight lead in polls heading into the back-to-back party conventions.

McCain's camp had shielded Palin from news media interviews until choosing Gibson and ABC to do the first one.

Critics have questioned her readiness to assume the president's job if something happens to McCain, a 72-year-old senator from Arizona. But she said she told McCain she was ready.