South Korean President Lee Myung-Bak arrived in Singapore Friday for a security forum at which he is expected to seek international support for punishing North Korea for the Cheonan warship sinking. Tensions have soared on the Korean peninsula since a probe concluded last month that a North Korean torpedo had sunk the South's naval vessel near their disputed sea border in March. Lee, whose arrival was confirmed by South Korea's embassy, was to deliver a keynote speech during a dinner opening the three-day forum, known as the Shangri-La Dialogue. Lee was expected to stress the gravity of Pyongyang's nuclear programme and call for international cooperation in 'resolutely responding to North Korea's provocation,' his spokeswoman, Kim Eun-Hye, told reporters in Seoul earlier. Lee's 20-minute speech will also cover South Korea's efforts to play a bigger role in the international community and its strategy for lasting peace on the peninsula, she said. The Cheonan sinking left 46 sailors dead and prompted Seoul to announce trade and other reprisals against Pyongyang. 