'It was a decisive victory after a long, hard battle,' PM Lee said in a letter to Mr Obama, the Democratic senator from Illinois who convincingly defeated Republican rival John McCain in the race for the White House.

'Many issues will claim your attention. May I make a case for the importance of Southeast Asia to the US, a region which is not unfamiliar to you,' Mr Lee said.

'The US has many friends and many interests in this region, which is happily not a problem region for the US. We can keep it that way.'

Analysts have said that US-Southeast Asia ties could see significant expansion if Obama won, as his advisors favour his participation in a key East Asian summit organised by the Association of Southeast Asian Nations and the expansion of US alliances in the region.

Mr Lee also told Mr Obama that 'the world needs a strong leader to overcome the deepening economic crisis, conclude the Doha Round of trade negotiations, achieve an international agreement on climate change and defeat terrorism'.

He said he looked forward to welcoming Mr Obama to Singapore in late 2009, when the Republic hosts the annual summit of Asia Pacific leaders.

He also sent a congratulatory letter to Senator Joe Biden, the vice-President elect.

"I admire your spirited campaign and was moved by your personal story of overcoming adversity," said Mr Lee.

" The world is at an important crossroad. Your experience as Chairman of the Senate Foreign Relations Committee puts you in a unique position to exercise leadership and help chart the way forward."

Mr Lee said Singapore and the US enjoy excellent relations, adding: " Our economic interlinkages are deep and multifaceted; and our defence cooperation substantive and mature. We share common perspectives on many international issues and work well together in international organisations."