* FIS wants longer doping ban for Norwegian
* IOC welcomes appeal, wants "clarity" before Pyeongchang 2018 (Updates with IOC reaction)
ZURICH, March 7 (Reuters) - The International Skiing Federation (FIS) asked for the 13-month doping ban on Norwegian cross-country skier and Olympic champion Therese Johaug to be increased, it said on Tuesday.
Johaug, who won the World Cup in 2014 and 2016 and has also won seven world championship titles and three Olympic medals, tested positive for the banned anabolic steroid clostebol while training in Italy last September.
The 28-year-old said she tested positive after using a cream to treat her sunburned lips bought by her doctor at an Italian pharmacy, without knowing it contained the substance.
Her 13-month ban was handed down by the Norwegian Olympic Committee last month. However, FIS said the ban was on "the low end of the range of reasonable sanctions" and that it had filed an appeal at the Court of Arbitration for Sport (CAS).
FIS said that Johaug "failed to read the doping warning label printed in red on the package despite the fact that the medication was unknown to her and was purchased in a foreign country".
The International Olympic Committee said it welcomed the FIS appeal as the matter concerned participation at next year's wither Olympics.
"The IOC has been following this case with great interest because it also concerns the participation in the Olympic Games Pyeongchang 2018," an IOC official said when asked by Reuters.
"Therefore the IOC welcomes and supports the FIS appeal because this will lead to clarity by the decision of the independent Court of Arbitration for Sport (CAS)."
"In this context the IOC re-emphasises its proposal to make the anti-doping testing and sanctioning system independent of both sports organisations and national interests."
Johaug won the gold medal in the 4x5km relay at the Vancouver Olympics in 2010 and also claimed a silver and bronze in Sochi four years later. She also won three golds at the 2015 world championships in Sweden. (Writing by Brian Homewood, Additional reporting by Karolos Grohmann; Editing by John O'Brien)