Repeated time values within panel

Hi!

I have a dataset that basically looks like this

country year var1 var2 var3 var4
1 1995 2 2 1 8
1 1996 5 5 2 5
1 1997 4 4 3 5
...
1 2012 4 4 4 7
2 1995 4 4 1 5
2 1996 7 5 9 7
2 1997 4 5 6 2
...
2 2012 5 6 8 2
3 1995 2 2 1 8
3 1996 5 5 2 5
3 1997 4 4 3 5
...
3 2012 5 6 8 2
etc.

In total i have 33 countries and 18 years. When I try to use 'xtset country year' command I get repeated time values within panel error. I think I undestand why I get this error, however I don't know how to fix it. I've tried searching for a solution on statalist but I can't find exactly what I'm looking for. Can anyone point me in the right direction?

Thanks in advance!