Keith Urban dedicated a Valentine's Day song to pregnant wife Nicole Kidman.

The country singer was playing in New York's Madison Square Garden when he performed his hit 'Got It Right This Time' in tribute to Nicole - who is currently in Australia.

He told the crowd on Wednesday: "It's Valentine's Day here tomorrow, but today it's already Valentine's Day in Australia."

The tribute ended a lively show for Keith, who at one point walked out into the crowd and played a song on his guitar before autographing the musical instrument and handing it to an audience member.

At the end of the show, Keith told the audience: "It won't take so long to come back this time. We'll be back in New York really soon."

Keith recently revealed he is planning on writing a song to dedicate to his first child when 'Moulin Rouge' star Nicole gives birth in July, adding: "It has been a really beautiful journey."