ST. PAUL, Minn. — John McCain's running mate Sarah Palin said Monday that her 17-year-old unmarried daughter is five months pregnant, an announcement campaign aides said was aimed at rebutting Internet rumors that Palin's youngest son, born in April, was actually her daughter's.

A statement released by the campaign said that Bristol Palin will keep her baby and marry the child's father. Bristol Palin's baby is due in late December.

"Our beautiful daughter Bristol came to us with news that as parents we knew would make her grow up faster than we had ever planned. We're proud of Bristol's decision to have her baby and even prouder to become grandparents," Sarah and Todd Palin said in the brief statement.

The disclosure of the pregnancy came on the opening day of the Republican National Convention, scaled back because of Hurricane Gustav, and three days after McCain named Palin as his running mate. Other news was likely to overshadow the disclosure.

"Bristol and the young man she will marry are going to realize very quickly the difficulties of raising a child, which is why they will have the love and support of our entire family," they added. The father was identified in the statement as Levi, but the campaign said it was not disclosing his last name or age.

The reactions of Utah delegates were sympathetic, not critical.

Lt. Gov. Gary Herbert said that he did not think it disqualified her to be

a vice-president, or that it should even be used politically.

"It's not a circumstance where I'd judge anybody," he said. "I trust that the party will give the Palin family their support."

He did applaud the daughter's decision to carry the baby and marry the father.

"Unfortunately, we have this problem all over the country," Herbert said. "It too often gets compounded by abortion."

Utah Senate Majority Leader Curt Bramble, R-Provo, said personal challenges happen to every family, and should never be used against the parents politically.

"Kids sometimes make bad decisions in good families," he said.

Sarah Palin's fifth child, a son named Trig, was born in April with Down syndrome. Internet bloggers have been suggesting that the child was actually born to Bristol Palin but that her mother, the 44-year-old Alaska governor, claimed to be the mother.

Palin spokesman Bill McAllister emphatically denied those rumors, and McCain adviser Mark Salter said the campaign announced the daughter's pregnancy to rebut them.

"Senator McCain's view is this is a private family matter. As parents, (the Palins) love their daughter unconditionally and are going to support their daughter," said McCain spokesman Steve Schmidt.