Alaska Governor Sarah Palin, Republican John McCain's running mate for the US presidency, has revealed that her teenage daughter is pregnant.
Mrs Palin, a social conservative who is opposed to abortion, said in a statement that her daughter Bristol, 17, would keep the child and marry its father.
Mrs Palin, a mother-of-five, was announced on Friday as her party's vice-presidential candidate.
The news comes as the Republicans' national convention is about to begin. The McCain campaign and Palins asked for respect for the couple's privacy.
Mrs Palin and her husband Todd said in a statement: "Bristol and the young man she will marry are going to realise very quickly the difficulties of raising a child, which is why they will have the love and support of our entire family."
Bristol is reportedly five months pregnant and is due to give birth in late December.
Advisers to the McCain campaign said they had known about the pregnancy before offering Mrs Palin the vice-presidential nomination.
"Senator McCain's view is this is a private family matter," Mr McCain's spokesman Steve Schmidt said. "As parents, [the Palins] love their daughter unconditionally and are going to support their daughter. Life happens."
Mrs Palin is due to be formally nominated by delegates as the party's vice-presidential choice later this week.
A BBC correspondent reports the news will certainly be a talking point but may not damage Mrs Palin's standing.
Mrs Palin was elected governor of Alaska in 2006, and before that was mayor of the small town of Wasilla, Alaska.