The Committee on Climate Change said it was "feasible but difficult" without a wider international agreement.

The panel also suggested the Scottish target could be lowered to 38% until a global deal was in place.

The Scottish government said it would continue to press other countries to act on climate change.

Legislation passed last year committed Scotland to reducing emissions by 42% by 2020 and 80% by 2050 - targets which are among the most ambitious in the world.

But the Committee on Climate Change - an independent group of scientists, academics and economists - said its analysis suggested achieving these cuts would be difficult without a wider commitment from other countries.

It said Scotland may consider less ambitious targets until an international agreement on cutting gas emissions was achieved.

Professor Jim Skea from the committee said: "A step change will be needed to unlock potential emissions reductions in Scotland, but we believe this to be achievable with new policies."

The Scottish government said achieving the necessary cuts would require hard decisions not only by government but businesses, the public sector, communities and individuals.

Climate Change Minister Stewart Stevenson said: "The need to take action to reduce our emissions is clear and everyone has a role to play in helping Scotland meet its world-leading climate change targets."

He added the Scottish government would continue talks to encourage other countries to increase their climate change ambitions.

'A cop-out'

But the Scottish Green Party said the lack of a global agreement could not be used as an excuse for not meeting targets.

Patrick Harvie MSP said: "Their advice to wait for international action will be read by many as an attempt to subvert the will of the Scottish Parliament and the Scottish people, and Ministers must not use this paper as an excuse for a cop-out."

Labour's environment spokeswoman Sarah Boyack accuse the SNP of not making enough progress.

She said: "Ministers need to launch a 'green new deal' to implement the practical measures in the Act such as council tax reductions for greener homes, support for people to install devices like mini wind-turbines and a public engagement strategy."

Alison McInnes MSP, the Scottish Liberal Democrat climate change spokeswoman, said: "To get to 42% it is vital that we take early action.

"The first set of annual targets will be announced in the next couple of months, so the government needs to step up and commit to wide-ranging measures aimed at reducing carbon emissions across every sector of the Scottish economy."

Meanwhile, Friends of the Earth Scotland called for other countries to follow Scotland's example on cutting emissions.

Chief executive Duncan McLaren said: "We believe the EU should commit to 40% and that the UK as a whole should join Scotland in committing to 42%."