San Francisco - A somber Barack Obama visited his ailing grandmother Friday in Hawaii, and told reporters that he feared that the woman who helped raise him would not live through election day.

"Without going through the details too much, she's gravely ill," Obama told ABC's Good Morning America. "You know, we weren't sure, and I'm still not sure, whether she makes it to election day. We're all praying, and we hope she does."

Obama flew to the island state Thursday night and went straight to visit Madelyn Dunham, 85, at the 10th-storey Honolulu apartment where he lived as a teenager. Television pictures showed a sombre candidate stepping from the plane with his hands in his pockets, walking straight to a waiting van without waving to supporters and cameras.

"I want to give her a kiss and a hug," Obama told ABC. "And then we're going to find out what chores I can do, because I'm sure there's been some stuff that's been left undone."

Obama paid a two-hour visit Friday to the woman he calls Toot - short for Tutu, the Hawaiian word for grandmother - and then took a short walk through the neighbourhood where he lived from the age of 10 to 18. He was forced to cut the walk short when reporters caught up with him, and he hopped backed into his Secret Service vehicle.

Obama said Thursday that he decided to take a break from the campaign to avoid repeating the tragic error of failing to make it back to Hawaii to see his mother, Dunham's daughter, Stanley Ann Dunham Soetoro, before she died of cancer in 1995 at the age of 52.

"(We) got there too late," he said in an interview with CBS. "We knew she wasn't doing well. But, you know, the diagnosis was such where we thought we had a little more time, and we didn't. And so I want to make sure that I don't - I don't make the same mistake twice."

Obama has often paid tribute to Madelyn Dunham and mentioned her strong influence on him when he accepted the Democratic nomination in September.

On Thursday, he again explained their special connection.

"My mother was a single mom, so she raised me with the help of my grandparents. And so my grandmother, my grandfather, my mom, they're really the people who - who took care of me all throughout my childhood," he said.

"My grandmother's the last one left. She has really been the rock of the family, the foundation of the family. Whatever strength, discipline that I have, it comes from her."

Asked whether he feared the impact of his break on the election campaign, Obama said that voters would understand.

"I think most people understand that if you're not caring for your family, then you're probably not the kind of person who's going to be caring for other people," he said.

Obama was due back to campaign Saturday in the battleground state of Nevada. In his absence, Obama's wife, Michelle, was campaigning in the hotly contested state of Ohio.

Independent analysts say that the trip could even play as an advantage to Obama, especially among seniors in key states like Florida. dpa