US President George W Bush has acknowledged that North Korea has addressed some of his government's concerns over its nuclear programme.
However, he said he remained concerned about North Korea's alleged enrichment of uranium.
Mr Bush was speaking following talks with the Japanese Prime Minister, Yasuo Fukuda, as the leaders of the world's major industrialised countries gathered in Japan for the G8 summit, which starts tomorrow.
The nuclear programmes in North Korea and Iran are expected to be on the agenda, as well as rising oil and food prices, climate change and the political crisis in Zimbabwe.
Mr Bush said North Korea had taken a number of positive steps but more were needed.
