John Key wasted little time tweeting a photo of himself chatting to United States President Barack Obama at the Nuclear Security Summit in South Korea yesterday.

The Prime MInister and Mr Obama spoke in the leaders' lounge before entering the summit, and the President later squeezed Mr Key's arm while walking past his chair in the hall.

The leaders of 54 countries have entered round-table talks about nuclear security and Mr Key said he would urge countries with nuclear stockpiles to go further to eliminate those materials.