Japan's foreign minister was preparing Friday to fly to Tehran where he hoped to leverage Tokyo's friendship and cement progress made in talks with world powers over curbing Iran's nuclear drive.
Fumio Kishida was set to leave Tokyo overnight Friday for a meeting with his Iranian opposite number on Saturday, along with a courtesy call on moderate president Hassan Rouhani.
Iranian Foreign Minister Mohammad Javad Zarif, who has been in talks with the so-called P5+1 in Geneva, said on Friday it may be possible to reach a deal that could see Tehran freeze its disputed nuclear programme in exchange for relief from crippling sanctions.
The issue will likely dominate meetings in Tehran, and Kishida is expected to press home the view that "Iran should respond to mounting international expectations of the Rouhani administration," a Japanese foreign ministry official said.
"As this window of opportunity is open for only a limited period, Iran should proactively show flexibility to solve the problem and restore trust among the international community," he said.
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Western powers suspect Iran's uranium enrichment programme is part of a plan to develop nuclear weapons. Tehran denies this and insists it is entirely peaceful.
Iran is anxious for relief from crippling economic sanctions that have cut oil revenues by more than half, caused the value of the rial to plunge and pushed inflation above 40 percent.
The West is also keen to seize a rare opportunity to build bridges with Iran after decades of hostility, opening the door to engaging with Tehran on other issues like the conflict in Syria, where Iran has backed President Bashar al-Assad against insurgents.
Japan, which is heavily dependent on Middle Eastern oil, has maintained friendly relations with Iran through its years of ostracism, keeping up a diplomatic two-way that many developed countries cut off decades ago.
But since Rouhani took office in August hopes have been raised of an end to the long-running crisis, especially after a round of hectic diplomacy during the UN General Assembly in September.
That set up a series of meetings, including the one in Geneva this week of the P5+1 -- the United States, Britain, France, China and Russia plus Germany.