SINGAPORE - Former US Secretary of State George Shultz has sent his condolences to Prime Minister Lee Hsien Loong on the passing of his father, Mr Lee Kuan Yew.

"I have always considered him one of the wisest and most intelligent people I have ever known. We met together many times and I was the better for it," he wrote.

"I often traveled to Singapore and, with all due respect to the appeal of the city, the real reason is to see Harry Lee."

"I am so glad that I was able to visit Singapore and see Harry once more in late 2013."

Dr Shultz and the late Mr Lee have known each other since 1973. They have worked on forging closer political and economic ties between the United States and South-east Asia for decades, and tap each other's views on global developments regularly.