US ambassador Louis B Susman last night told a business audience at Edinburgh Castle that Scotland is a "crucial player" in transatlantic commercial links between America and the UK and an "attractive investment opportunity".

Mr Susman also told the British-American Business Council (BABC) transatlantic dinner, to which First Minister Alex Salmond was invited, that he had "no intention this evening of entering the domestic political arena".

The US ambassador added: "In particular, Alex, I will not get into the thorny issue of Scottish independence - even though an American undoubtedly brings immense experience to any debate about independence from the United Kingdom."

Mr Susman last night cited the "stagnant economy here in the United Kingdom and the turmoil in the eurozone" as "two substantive current challenges".

He meanwhile highlighted the fact that the US economy had "grown every quarter since mid-2009", and that its "trend lines continue to be strong", as he took issue with claims from some authors, academics and commentators that America was in decline.

Mr Susman also declared that the future prosperity of the global economy rested on the resolution of "complex, intense, and accelerating" issues in the eurozone.

He said: "The United States is rooting for rapid recovery in the United Kingdom and a lasting solution to the troubling crisis in Europe."

Mr Susman told his audience that the US-UK alliance was the "most powerful partnership the world has ever known", and declared the commercial component was and always had been one of the most important elements of this critical relationship.

He said: "It is good to remind ourselves that United States-United Kingdom trade remains vibrant, that our investment ties are still the largest in the world, and that this relationship supports one million jobs in each country."

Mr Susman added: "I do not have to call to your attention – but I will – that Scotland is a crucial player in these transatlantic commercial links. The success of its own companies and its skilled and highly- effective workforce makes it an attractive investment opportunity.

"That being said, the relationship goes both ways. American corporations operating here do more than just invest in businesses and equipment, they invest in this country's greatest resource: its people. Tonight I thank all those in this room who work to reinforce our economic ties by exchanging capital, goods and ideas on a daily basis."

Mr Susman meanwhile acknowledged the work of the Scottish North American Business Council, the Scottish chapter of the BABC.

Turning to the US economy, Mr Susman said: "In regards to the United States, I have noticed a trend among some authors, academics and commentators declaring that America is in decline. The argument goes that a gradual but irreversible erosion of economic superiority, and the effects of two gruelling wars is stripping the United States of its power, influence and authority.

"Nothing could be further from the truth. I believe emphatically that America is not in decline."

He added: " Now, there's no doubt that the global order is being reshaped and that America faces undeniable challenges. But we have overcome similar circumstances before. In the 1950s and 60s the fear was we were falling behind the Soviet Union in technology and ambition.

"The 1970s brought recession and unemployment to America; combined with a loss of faith in our system after Vietnam and Watergate. At the same time, Japan's economy was taking off. Then, in the 1980s and 90s, the tiger economies of East Asia produced an economic miracle of rapid growth unparalleled in modern history."

Mr Susman observed that, each time, "America's standing was being questioned".

But he declared: "Each time, America rose to the particular challenges it faced. Time and time again the doom-mongers and the defeatists were proven wrong. And I am confident that they will be again..."

Mr Susman added: "Despite being damaged by the most severe recession in more than 70 years, America is still – by far – the world's largest economy. Today, the United States is responsible for one-quarter of all global economic output, just as we have been for more than four decades."