U.S. President Barack Obama arrived in Seoul on Wednesday ahead of a Group of 20 (G20) summit due to start the following day in the South Korean capital.

Mr. Obama left Indonesia, one of his stops on his 10—day tour of Asia, several hours earlier than scheduled because of fears that ash from the erupting Mount Merapi volcano, 500 kilometres south—east of Jakarta, could disrupt flights.

The U.S. president was preceded by several leaders of the world’s 20 leading economies, among them Russian President Dmitry Medvedev, Australian Prime Minister Julia Gillard and South African President Jacob Zuma, who had arrived in Seoul earlier in the day. Others, including G20 veteran Silvio Berlusconi of Italy, were due to arrive a day later.

Thursday will see a flurry of bilateral meetings ahead of the G20, which kicks off with a working dinner on the global economy in the evening.

Much of the talking will focus on trade imbalances and a currency war that risks hampering the fragile global economic recovery.

But South Korean President Lee Myung Bak has said it was unlikely that the summit will agree on specific guidelines on easing such balance of payments imbalances. The G20 members were establishing a working group on the issue that would take at least “four to five months” to complete its work, Mr. Lee told the JoongAng Ilbo newspaper earlier this week. Security was high ahead of a protest planned for Thursday in central Seoul, with thousands of demonstrators expected. The government has mobilized some 50,000 police and 10,000 soldiers, more than double the security presence at the previous G20 meeting in Toronto.

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