US President Donald Trump indicated the "significant influence" John Swinney had on the removal of tariffs on Scotch whisky, the First Minister has claimed.
Mr Trump announced the move on social media on Thursday night, saying the 10% levy would be scrapped and indicating it was the King who had pushed the deal over the line.
A message from the president had been sent to Mr Swinney ahead of the announcement, which the First Minister said suggested his own influence on the move.
Mr Swinney pushed hard last year for the tariffs to be scrapped - pointing to the cross-Atlantic trade in whisky casks hitting the industry in both Scotland and states like Kentucky - including during a meeting in the White House.
During a visit to Deanston Distillery near Stirling on Friday, Mr Swinney told the Press Association: "The president indicates to me in his note the significant influence on his thinking of the Kentucky-Scotland deal, as he puts it, and he references that in his post on social media last night."
The First Minister said he had helped to put the issue of whisky tariffs on the president's radar last year when they met at his golf course in Aberdeenshire.
"I used that moment to put forward the arguments that there was a direct impact on Scotch whisky that has been followed up by the proposal in relation to the economic damage done to Scotch whisky, the economic damage done to the cask industry in Kentucky, which affects American jobs and livelihoods," he said.
"That's the argument that President Trump cites in his announcement last night as being the argument which has persuaded him to lift the tariffs."
Mr Swinney said he is "delighted" the tariffs are being lifted, as he welcomed the involvement of the King, who visited the US this week.
He also welcomed the involvement of the UK Government - but Scottish Secretary Douglas Alexander has hit out at the First Minister for claiming credit.
Mr Alexander told LBC that the contention Mr Swinney had brought the issue of whisky tariffs to the president's attention was a "lie", adding the First Minister had been "caught red-handed" claiming credit for a deal that was secured by the King.
Mr Swinney told PA the Scottish Secretary - who is the co-chair of Scottish Labour's election campaign - was "demonstrating a desperation in his behaviour".
The First Minister said: "I understand people's emotions are raw and they're under a lot of pressure and under a lot of stress.
"But I think Douglas Alexander really lets himself down with the way he speaks about other people and I don't understand why he's doing that."
He later told journalists the relationship between the Scottish and UK governments had soured in recent months, and he traced it back to Mr Alexander's appointment as Scottish Secretary in September.
Earlier on Friday, Scotch Whisky Association head of strategy and communications Graeme Littlejohn said the tariffs announcement was the result of "months and months of work", adding: "The King was the royal sparkle at the end of a lot of work to get a deal over the line here; this doesn't happen overnight."
He added: "The fact that these tariffs are now going to be removed... is a real boost for the industry, and distillers will breathe a little easier during a time of significant pressure on the industry."
"The impact of these tariffs has been significant; the US is the industry's largest global market—around 20% of global exports of Scotch whisky goes to the United States—around £1 billion a year."
"Any tariff into a market of that size is going to have a significant impact. This tariff has definitely cost jobs; it has definitely paused investment in the industry; and it has definitely been a significant period of strain on the industry."
Charandeep Singh, chief executive of the Scottish Chambers of Commerce, also welcomed the news and said it will "deliver major benefits both sides of the Atlantic".
He added: "We know from extensive discussions during our own recent trade visit to the USA that an enormous amount of work has been going on behind the scenes to bring about this change - and credit is very much due to the whisky industry and both Scottish and UK governments for their determined efforts.
"The USA is the most important export market for Scotch, worth close to £1 billion, and it's a wonderful way to round off this week's state visit with His Majesty the King sealing a great deal for the sector.
"We should raise a glass following President Trump's announcement - and look forward to further strengthening the special business relationships between our economies."