There have been diplomatic talks for four years, and they haven't gotten anywhere. The OSCE has what's called the trilateral contact group, which includes Russia, Ukraine, and the OSCE. There is also what are called the Normandy talks, which is Germany, France, Ukraine, and Russia.
The OSCE process produced the Minsk accords. The first point of the Minsk accords is a ceasefire, which was signed three years ago, and I don't think there have been more than a dozen days in three years when there has been no fighting.
These diplomatic efforts have to be undertaken from a position of strength by the west, and the way to get to that is to increase pressure on the Russians in order to force them to make a deal. It is pretty obvious that right now they're not feeling enough pressure to make a deal, because it's been four years of fighting. Diplomacy that isn't backed up with credible strength is ineffective, as we can see from these past four years.