U.S. Republican's presumptive presidential nominee John McCain defended his selection of Alaska Governor Sarah Palin as his running mate on Tuesday despite controversy caused by her teenager daughter's pregnancy.

US Republican presidential candidate Senator John McCain looks on as his vice presidential running mate, Alaska Governor Sarah Palin (R) gestures to the crowd at a campaign event in Dayton, Ohio August 29, 2008. [Xinhua/Reuters Photo]

"My vetting process was completely thorough and I'm grateful for the results," McCain told reporters as he campaigned in Philadelphia.

His comments came one day after Palin and her husband announced that their 17-year-old daughter, Bristol, was 5-month pregnant and would marry the child's father.

"America's excited and they're going to be even more excited once they see her tomorrow night," the Arizona senator said in another stop in Ohio. "I'm very, very proud of the impression that she's made on all of America and I'm looking forward to serving with her."

Palin's selection stirred more controversy after disclosure that she had hired a private lawyer in an ethics probe in Alaska, and feed doubts on McCain's judgment and how thoroughly her background was examined.

McCain's campaign has been trying to defend their vice president vetting procedure since Palin was announced as his running mate on Aug. 29.

According to a timeline issued by the campaign, McCain met Palin for the first time in February, and then had a telephone conversation with her last week before inviting her to Arizona, where he met with her a second time and offered her the job Thursday.

The campaign also said that Palin's husband, Todd, was arrested in 1986 in Alaska for driving under the influence of alcohol, at age 22.

McCain and Palin were due to officially receive their nominations during the Republican National Convention currently held in Minnesota.

US Republican presidential candidate Senator John McCain (2nd R) and his wife Cindy (R) head in for a shopping trip at The Buckeye Corner in Columbus, Ohio, with running mate Alaska Governor Sarah Palin (3rd L), her husband Todd (L) and their daughters Piper (3rd R) and Willow (2nd L) August 29, 2008. [Xinhua/Reuters Photo]

(Xinhua News Agency September 3, 2008)