David Axelrod, the American political campaigns guru who Ed Miliband has employed as a key strategist for the general election, remains actively involved in advising Labour, he has told the Guardian.

Axelrod has been the subject of rising speculation about his low visibility in the UK as the 7 May ballot approaches. Last week, the Sun went as far as to suggest that he had decided to be done with the Labour campaign.

But in an interview with the Guardian in New York for his new autobiography, Believer, Axelrod insisted that he was, and would continue to be, a part of Miliband’s strategic team for the 7 May election. “I’ve been [in the UK] for visits in the last couple of months; I’ll be going back. I think it’s less about me being there as a showpiece than about what strategic insights can I offer,” he said.

He admitted he was “a little tied up now” with a publicity drive for his book that is expected to last a month. “This was an understanding I had with Miliband”, he said.

Believer tells the story of Axelrod’s 40 years in politics, starting with his political awakening as a child when he heard John F Kennedy speak and ending with Obama’s 2012 re-election. It does not mention Miliband in the course of its 500 pages.

Axelrod was signed up by Miliband last April for a reported six-figure sum amid considerable fanfare. As a central figure in the campaign to elect Barack Obama as US president in 2008, as well as in his re-election campaign four years later, Axelrod is one of the most sought-after election wizards in the world.

On the eve of his 60th birthday, he said he had no intention of leaping back into the 2016 presidential race in the United States. “Even as a young man I said I’m not going to do campaigns after the age of 60. I saw people who did that and the toll that it had taken.”

His great strength is helping candidates boil down their personal stories and political priorities into clear narratives that can win over undecided voters. He calls himself “Keeper of the Message”.

Since his appointment to the inner team that is devising Labour’s election strategy, he has been notable more for his absence in the UK than for his impact on the party’s thinking. By contrast, his old friend and colleague in the Obama administration, Jim Messina, has been more visibly present in an equivalent role advising David Cameron and the Conservative election team.

In November, for instance, Messina addressed Tory MPs at their awayday in the Cotswolds and told them: “I’ve never, ever lost an election in my life and I’m not going to start with Ed Miliband.”

In his Guardian interview, Axelrod tried to deflect criticism that he is only semi-engaged in the Labour battle to unseat the Tory-Liberal Democrat coalition. He said that two other US colleagues from his former firm AKPD – Californian consultant Larry Grisolano and Mike Donilon, former senior adviser to the US vice-president Joe Biden – were also involved alongside him in advising Miliband.

He said the focus on him and on his old friend and now rival Messina was misplaced. “A lot of people want to make this about him and me. It’s not.”

One of the criticisms that has been raised about the involvement of the “Yanks”, as the Daily Mail put it, in the UK election is that the US electoral system is so different. Axelrod agreed that the prohibition of political TV advertising in Britain was a huge difference with his native country, where the 2008 and 2012 presidential elections were both awash with TV ads paid for largely by outside interests.

“The challenge in Britain is that you don’t have paid media, so you are at the mercy of earned media – of the press. And that’s a very dirty filter through which to communicate,” he said.

Axelrod said that Miliband’s challenge of selling his vision to voters will become much easier when the general election campaign proper begins. “He will be in front of the media in a short campaign. The fact that [David Cameron] is so eager to avoid debates or make them non-events reflects that he knows that Ed Miliband can be an appealing candidate if he gets the opportunity – and he will in the final push.”

Axelrod predicted the election would be “very close and competitive”.

In a tight race, Axelrod’s brilliance at devising simple but powerful messages could prove extremely useful to Labour as the party seeks to win over voters. He has a far more illustrious reputation for such message-creation than Messina.

But there still appears to be much work to be done. Messina has already boiled down the Tory offering to six words: ““Cameron is fixing Britain, creating jobs.”

When the Guardian asked Axelrod to do the same for Labour, he replied with a 145-word answer.