THE 1000-plus American companies that operate in Scotland will have to reassess their position if Scotland were to become independent, President Obama's ambassador to the UK said yesterday.

However, Louis B Susman also highlighted the fact the US is by far Scotland’s single largest trading partner and, with the “exception of (Abdelbaset Ali Mohmed al) Megrahi ”, the man convicted of the Lockerbie bombing, the “relationship between Scotland and the US has been ... pretty good”.

During his interview with The Herald in Edinburgh yesterday, Mr Susman, who was vice-chairman of Citigroup Corporate and Investment Banking until being appointed US Ambassador to the Court of St James in 2009, also rebuffed claims that US companies were mere fairweather friends to Scotland, which often made large scale redundancies before quitting the country when the subsidies ran dry.

Asked about the prospects for American companies in a hypothetically independent Scotland, given First Minister Alex Salmond’s recent claims that a majority in a referendum would be mandate for independence, Mr Susman said: “For diplomatic reasons, I have seriously kept out the internal politics of the UK, and Scotland in particular. That is a matter for the people and their governments.”

However, he added: “I believe the enticement of the high-quality workforce here and the fact that this is a very good place to live is likely to continue.

“In the event of independence, the situation at the time will have to be assessed.

“US companies will have to look to see where they will be in terms of things like tax policy and immigration, for example.

“At that point, we’ll just have to wait and see what happens.”

Over the years, a long list of US companies -- including Motorola, its descendant Freescale, HP and electronics design company Cadence -- have abandoned or drastically slimmed down operations in Scotland as economic tides turned.

When asked about the criticism, Mr Susman said: “I reject that position. Look at companies like GE, Raytheon and IBM, which have been here for years. They have all made massive investments in Scotland.

“Of course, some companies felt they made mistakes by coming to Scotland and pulled out, but there is no trend.

“There are about 1000 American companies in Scotland. The relationship between America and Scotland has been generally pretty good, with the exception of Megrahi.”

He added: “But it’s not just about American companies in Scotland. America is a huge trading partner for Scotland.

“We also love to have Scottish companies invest in the US, and there are quite a few, companies like Craneware, for example. The Scotch whisky industry is also doing pretty good.”

Mr Susman, who was in Scotland to give a speech last night to Edinburgh University students, also met Scottish Finance Minister John Swinney, whom he described as “a very impressive man”.

He said he and Mr Swinney had discussed “the economy” and said his “ideas on policy and the economic situation” were “also impressive”. He described First Minister Alex Salmond as “an excellent politician”.

In terms of the global economy, he said European politicians must “create a firewall” around Greece to stop the “contagion”.

Asked about concern over the rise of China’s economy, he said: “It’s not a foregone conclusion that China will dominate the world economy. It’s clear they want to rise, but a lot of things can happen. Years ago, everyone said Germany and Japan would rule the world. Well, that hasn’t happened.”

Referring to China’s undervalued currency, he added: “It’s easy to rise when you don’t float your currency, but they are already seeing slower growth, inflation and unemployment.”

While Mr Susman, 73, has been a lawyer, banker and a power figure in Chicago’s financial district, he also has a track record of being highly political himself. He raised funds for Ted Kennedy’s challenge to Jimmy Carter for the Democratic Party nomination in 1980.

And, as John Kerry’s national finance chairman during his 2004 presidential bid, Mr Susman was so tenacious a fundraiser he was nicknamed “The Vacuum Cleaner” -- in reference to his ability to suck cash from the pockets of would-be sponsors.

He drummed up $247,000 for Barack Obama’s presidential campaign and a further $300,000 for his inauguration.

Plum ambassadorships often go to friends and fundraisers, and US Ambassador to Britain is one of the plummiest.

Mr Susman was asked if he agreed with US Secretary of State Hillary Clinton that Megrahi should be returned to a Scottish jail in the wake of Muammar Gaddafi’s death.

A Scottish court sitting in The Hague found Megrahi guilty of the bombing of Pan Am Flight 103 in 1988, which killed 270 people in the worst terrorist attack over UK soil. However, Megrahi was released by Scottish ministers who said that medical advice suggested his terminal prostate cancer meant he had just three months to live.

Mr Susman said: “I always agree with my boss.”