The 29-year-old beat his rivals in both the 100m and 200m breaststroke finals at the National Championships last week, which served as Olympic trials for Japanese swimmers.

He told a news conference after the Japan Swimming Federation formally announced its Olympic squad: "The fact that I could demonstrate what I had under such pressure has helped me remove fears about going to the world.

"I am confident of overcoming such pressure on the basis of my experience," said Kitajima, who retained the 100m and 200m breaststroke titles at the 2008 Beijing Games.

Record

He added: "I think I will just prepare myself to be able to stand on the starting block with my head held high."

At the Nationals, he won the 100m breaststroke in a Japanese record of 58.90 seconds, ahead of Asian Games champion Ryo Tateishi, who clocked 59.60.

In the 200m, Kitajima clocked 2:08.00, the world's fastest time since special swimsuits were banned in 2010.

Kitajima was selected for the 27-strong squad of 13 men and 14 women. London will be his fourth Olympics since his debut at the Sydney Games in 2000 where he finished fourth in the 100m.

Thrills and nerves

For 17 members of the Japanese team, it will be their first Olympics.

Responding to a question on the possibility of his winning another double in London, he said: "As long as I have a chance, I will go for it."

Asked on what motivates him to carry on his long-running career he replied: "Because I enjoy it. I enjoy the thrills and nerves of being a challenger."

One of Kitajima's biggest rivals for the gold medal will be Norway's Alexander Dale Oen, who won the 100m at last year's World Championships when Kitajima finished fourth.

"If it comes down to me and Dale Oen, I've got to find a way to get in his head," Kitajima said of his Scandinavian rival according to Kyodo news agency.

At Beijing, the Norwegian came second behind Kitajima.

"It'll be difficult because he's mentally tough. But I like to think my time at the championships caught his attention."

Also on the squad are Takeshi Matsuda, who finished runner-up to American Michael Phelps in the men's 200m butterfly at the worlds, and world 200m backstroke silver medallist Ryosuke Irie.