* Norway 2018 output seen as "high and stable" as in 2017
* Norway can meet UK gas needs despite Rough storage issues
* Gassco is working on Norway-Denmark pipeline concept study
* Pipeline to the Arctic gas fields cost now seen lower (Adds quotes, background)
By Lefteris Karagiannopoulos
OSLO, June 7 (Reuters) - Norway will deliver at least the same amount of gas by pipeline in 2017 as it did last year, when output was 108 billion cubic meters, the chief executive of Gassco, Norway's gas infrastructure operator, told Reuters.
Norway is Western Europe's largest gas exporter and Britain's top gas supplier, covering 40 percent of the country's gas needs in 2015.
"It is fair to assume that we will stay at the same high levels as we did in 2016 ... at least the same level," Frode Leversund said in an interview, adding that in 2018 Norway could deliver the same "high and stable" volumes as in 2017.
Concerns about the reliability of Britain's gas supply has increased since operator Centrica said its largest natural gas storage site, Rough, will not be able to receive any gas supplies until April next year.
The Gassco CEO said Norway could meet Britain's gas needs regardless of the Rough issue. "We are in a position to deliver to the UK what it needs ... if you need the gas, the system is available to deliver the gas," he said.
While no further capacity upgrades are expected at any of Norway's gas processing plants, Gassco has plans to enhance the technical integrity of the plants by improving its ageing systems.
"We have launched a big project now at Kaarstoe, for example. It costs about 800 million crowns ($94 million). These projects will be linked to the regular maintenance of the plants," Leversund said, adding that ongoing maintenance at Norwegian gas installations was going to plan.
Poland wants to build a gas pipeline from Norway via Denmark so it can lower its dependence on Russian gas. Warsaw and Copenhagen are launching a key survey this week to determine the demand for the part connecting Denmark and Poland.
Leversund said Gassco had received a request from Denmark's power and gas infrastructure operator to work on a concept study on its behalf for the part between Norway and Denmark and that it would finalise the study in the first quarter of 2018.
Gassco also said the cost of a pipeline to connect Arctic fields to Norway's existing gas infrastructure was now lower than a 2014 estimate of 24 billion crowns.
"The cost will be lower. The potential is there, absolutely ... That could be after 2020," he said, without giving a new estimate.
A number of oil firms are exploring for hydrocarbons in the Arctic and a pipeline is one of several options under consideration to transport any gas found. (Editing by Gwladys Fouche and David Clarke)