SEOUL (Reuters) - U.S. President Barack Obama warned North Korea on Friday against conducting another nuclear test, saying that it would draw a firm international response.

"If North Korea were to make the mistake of engaging in another nuclear test, it should expect a firm response from the international community," Obama said in an interview with the JoongAng Ilbo newspaper.

Obama arrived in Seoul on Friday for a visit in which he will seek to reassure South Korea that he is committed to pressuring Pyongyang to abandon its nuclear ambitions.

Although North Korea has ramped up provocative behaviour in recent weeks with talk of a new type of nuclear test and a flurry of rocket launches, South Koreans have been preoccupied with one of the worst tragedies in their history, the sinking of a ferry carrying hundreds of youngsters to a vacation idyll.

"I know my visit now comes as South Koreans are in mourning and my visit will be an opportunity to express the sympathy of the American people," Obama said.

The U.S. president arrives in Seoul after starting an four-stop Asia tour in Tokyo on Wednesday. He is also due to visit Malaysia and the Philippines.

(Reporting by Mark Felsenthal; Editing by Paul Tait and Simon Cameron-Moore)