The Group of Eight foreign ministers will urge Iran this week to accept a proposal for talks on its nuclear drive unless Tehran responds first, a Japanese official said on Monday.
Foreign ministers from the Group of Eight industrialised nations will meet on Thursday in Russia to prepare for a summit next month, with the crises over North Korea and Iran set to feature on the agenda.
"If we do not receive some positive response from the Iranian side by the date of the foreign ministers' meeting, I guess the G8 will strongly urge the Iranian government to respond quickly and positively to the offer," the foreign ministry official said.
The five permanent UN Security Council members -- Britain, China, France, Russia and the United States -- plus Germany offered the package in mid-June offering incentives and multilateral talks to Iran.
Tehran in exchange would have to temporarily halt uranium enrichment activities, which lie at the heart of fears the Islamic republic could develop nuclear weapons.
The six countries asked Iran to respond by the end of the month, but President Mahmoud Ahmadinejad said Tehran would wait until August 22 to give a formal answer.
"We (the G8) as a group are supporting the six countries' negotiations," the Japanese official said.
Japan has maintained close ties with Iran despite the crisis and is a top investor in its oil industry.
The G8 foreign ministers will also discuss North Korea, a self-declared nuclear power, which is feared to be set to launch a long-range missile.
Japan will "take a lead and brief on the current state of the North Korean nuclear issue as well as the abduction and missile issues and ask for the understanding and support of G8 countries," the official said.
Japan has been campaigning for more international pressure on North Korea to better account for Japanese civilians the regime kidnapped in the 1970s and 1980s to train its spies.
Japanese Foreign Minister Taro Aso will also hold bilateral talks with Russia and go to Ukraine during his visit.