Owen Kelly, the chief executive of trade body Scottish Financial Enterprise (SFE), has warned that it would be "an enormous missed opportunity" for Scotland if financial services are excluded from the controversial transatlantic trade pact currently under negotiation.

After almost two years of deliberation the eighth round of talks aimed at establishing a Transatlantic Trade and Investment Partnership (TTIP) between the EU and the US got underway in Brussels last week.

At stake is the creation of a free trade area that has been talked about for 12 years which proponents argue could boost the EU and US economies by 0.5 percentage points a year, adding an annual €120 billion to the EU economy and £10bn to the UK economy.

The Centre for Economy Policy Research think-tank believes that the three sectors of the UK economy that are most likely to benefit from an EU-US trade accord are the automobile industry, financial services and chemicals.

But, although the automobile and chemicals sector will definitely be included in the deal, US negotiators - under pressure from Republican politicians - spent much of last year opposing the inclusion of financial regulation in the proposed trade pact amid mounting pressure from the EU and lobbying by the financial industry to include it.

If financial services are not included in the deal the industry on both sides of the Atlantic would be left out of what has the potential to be the largest trade deal ever concluded which would account for 60% of total global output and create a market of 820 million consumers.

According to Kelly, the consequences for Scotland's financial sector would be a sizeable reduction in the commercial opportunities for Scotland's asset management and pension companies in the lucrative US market. UK banks and insurers would also be affected.

"We are good at financial services in the UK," Kelly said. "We are strong supporters of the single market in the EU and TTIP would open up a similar trade area for financial services across the US."

Along with the SFE, TheCityUK, the UK-wide trade body for financial services, is also pushing for financial services to be included in the EU-US trade deal.

Director of international strategy Gary Campkin said that the UK now has a "generational opportunity to create a really effective transatlantic market place" which would "improve regulatory coherence and reduce costs for businesses".

According to Campkin, the real value of the trade pact does not lie in the abolishing of already low import tariffs - averaging around 3 per cent - but in the dismantling of non-tariff barriers, such as the fact that in the US, insurance is regulated at a state level.

But, if financial services are ultimately included in the deal, there are questions over whether it would significantly affect firms with well established business in the US. Companies that have already set up registered companies in the US might find that TTIP makes little difference to their strategic ambitions.

Nick Thomas, a partner with Edinburgh-based fund managers Baillie Gifford, said that including financial services in TTIP would probably make it easier for firms considering a move into the US market but could have a limited impact on firms - such as Standard Life or Baillie Gifford - with an already strong presence in the States.

Baillie Gifford already manages £42bn, around a third of the company's business, for US clients through its New York office. "This trade deal could reduce the regulatory headwinds for start-ups thinking of moving into the North American market," he said.

The commercial opportunities of TTIP for the Scottish economy were underlined by the finance and economy cabinet secretary John Swinney when he appeared before the Scottish Parliament's European and External Affairs Committee on Thursday. With Scottish exports to the US totalling £3.9 billion in 2013, the US is already Scotland's second most important export partner after the EU.

"TTIP gives us the opportunity to build on that relationship," Swinney told parliamentarians. "It could provide better access to and for Scottish goods and services."

But the Deputy First Minister cautioned that the economic benefits of TTIP had to be balanced against the need to protect public services such as the NHS. Any trade deal is "not a one-way street" he said and should be approached with "eyes wide open".

Fears that public services such as the NHS could be undermined by a trade deal between the EU and the US have been dismissed as scaremongering by David Watt, the director of the Institute of Directors Scotland, who believes that it has "hijacked" the more important issue of finalising a deal that would open up the north American market for Scottish exporters and bolster growth.

"A widening of the market place can't be anything but good for Scotland and for Scottish jobs," Watt said. "Scotland has a very low level of exporting and we need to do something about that."

In addition to the financial sector, Watt believes that the Scotland's food and drink industry (including whisky), manufacturers, energy and technology companies would all benefit from a successfully concluded TTIP.