FORMER US secretary of state Henry Kissinger has said he would not welcome the United Kingdom getting smaller.

Mr Kissinger, former national security adviser and secretary of state under presidents Richard Nixon and Gerald Ford, said he has no strong views on the technical issues of the Scottish independence referendum. But he remains a strong advocate of Britain's nuclear capability - which is based in Scotland - and its role in global strategy.

"I have always been a strong advocate of the special relationship," he told Prospect magazine. "Not so much because of the power of Britain but because I thought it was important for America and important for the structure of the world to have another country that independently designed its policy but - because of its own convictions and a maybe different tradition of foreign policy - worked on common conclusions.

"I thought that that was important for us who would otherwise be stuck as an island between Eurasia and Europe. That's why I've been in favour of a nuclear capability for Britain because I wanted Britain to be recognised as a significant country in terms of global strategy.

"So anything that makes it smaller, I cannot say I welcome ... (but) I have no strong views about the specific technical issues on which much of the referendum debate is taking place."

A full account of the 90-minute interview will appear in the October issue of Prospect, in which Mr Kissinger also discusses Russian president Vladimir Putin, US president Barack Obama's diplomatic skills and the US's relationship with Iran.