Rose Byrne as Diana Wayland and Nicolas Cage as John Koestler.

I Love You, Man, which came in second.

The film, starring Paul Rudd, Jason Segel, Rashida Jones, Sarah Burns and Jaime Pressly, debuted at $18 million (£12.5 million), while Julia Roberts' spy thriller Duplicity opened in the third spot with $14 million (£9.7 million).

Dropping from number one to the fourth spot is Disney movie Race to Witch Mountain, starring former wrestler Dwayne 'The Rock' Johnson, taking in another $13 million (£9 million) in its second week.

Rounding out the top five is superhero film Watchmen, which fell from the second spot, earning another $6.7 million (£4.6 million) at the weekend. The film boasts a three-week total of $98 million (£68 million).

Source: WENN