Shia LaBeouf admits he’s the luckiest guy in the world after kissing both US star Megan Fox and Aussie actress Isabel Lucas in the latest Transformers movie.

But the 22-year-old actor wisely opted not to disclose which kiss was better at a news conference for Transformers: Revenge of the Fallen in Tokyo on Tuesday.

“Oh Christ, thank you, I appreciate that question,” deadpanned LaBeouf, who was flanked on stage by the two beauties.

“It’s incomparable, they are both specimens cut out of stone.

“I’m the luckiest dude in the world clearly. Anything beyond these answers and I start getting in trouble.”

In the movie, which is out in Australia on June 24, LaBeouf reprises the role of Sam Witwicky, the human caught in the war between autobots and decepticons, and Fox returns as his girlfriend Mikaela.

Lucas plays Alice, a girl Sam meets at college.

The former Home and Away star said she always feels nervous filming a kissing scene but knowing the other person helps.

“Shia’s become a really good friend,” Lucas told the room full of media.

“It’s always kind of awkward doing kissing scenes, you’re nervous and you’ve got 200 people there.”

But there was no such awkwardness from sexy star Fox.

“I didn’t think it was awkward at all. I love kissing Shia,” she said playfully, causing LaBeouf to blush.

On Monday night, LaBeouf, Fox and Lucas helped director Michael Bay unveil the film at the world premiere in the Japanese capital.

It’s Lucas’ first trip back to Japan since she fled the country in November 2007 when her anti-whaling activities got her in trouble with the police.

She was part of a group of 30 people from Sea Shepherd Conservation Society who took part in a protest against the slaughter of pilot whales in the coastal town of Taiji in Japan, and a warrant was issued for her arrest.

At the time, Lucas admitted she could be arrested if she ever returned to Japan, but she told AAP she hadn’t had any trouble this time.

“There hasn’t been any negative repercussions here,” she said.

“I think it would just draw so much more attention to the issue and I personally think it would be a good thing because it is something I’m very passionate about still.

Lucas said she was enjoying being in Japan and wanted to be respectful of Japanese culture, but didn’t rule out taking part in future anti-whaling activity.

“We’re still considering different ideas and ways to approach it and to take further action, but at this stage I’m referring everyone to the Whaleman Foundation to go to www.socialvibe.com and we’re trying to get over a million signatures to present to the International Whaling Commission meeting at the end of June,” she said.