The SNP has pledged to carry out a feasibility study on extending the Borders Railway, possibly to Carlisle, if re-elected in May.
Nicola Sturgeon made the commitment during a campaign visit to Hawick, as she also promised that every home and business in Scotland will have access to superfast broadband under an SNP government.
The £353 million Borders Railway, which runs from Edinburgh to Tweedbank, was opened by The Queen in September last year.
Passenger numbers on the route have already surpassed 500,000.
Last month Scotrail announced that the Borders Railway would undergo an increase in seat numbers and hourly connections with stations to the west of Edinburgh.
Ms Sturgeon said a re-elected SNP government would look into the possibility of extending the line past Tweedbank as far as Carlisle.
The SNP leader said: “The Borders Railway has been a fantastic success, boosting the economy, leading to new house building and supporting tourism in the region.
“Since it was opened last September the number of passengers has exceeded all expectations, with over half a million people travelling on the line by January.
“With this kind of success it makes sense to look at extending the line to other communities. I know there is support across the Borders for extending the line to Carlisle, and if re-elected we will take the first step on that journey.
“Creating greater connectivity between businesses and communities in the Scottish Borders and the rest of the Scottish economy is key to growing the economy of the south of Scotland.”
The Waverley Line, between Edinburgh and Carlisle, closed in 1969.
In 1999, the then Scottish Executive commissioned a feasibility study into its re-opening, marking the start of lengthy construction process.
On September 9, 2015, Her Majesty the Queen cut the opening ribbon on the day she became Britain’s longest-serving monarch. Celebratory events were held in communities along the line.
Ms Sturgeon also pledged to increase digital connectivity to 100 per cent of homes and businesses to boost the rural economy. Broadband has been delivered to 85 per cent of premises in Scotland, with the target of delivering to 95 per cent by the end of 2017 on track, she said.
The SNP would use “innovative schemes, new technologies and provide financial backing” to deliver broadband to the remaining five per cent of homes and businesses over the next parliament, she said.
Ms Sturgeon said: “Greater connectivity, through better transport links and improved digital infrastructure, can ensure that all parts of Scotland can reap the benefits of economic progress.”