Ashdown sent the message to the media via e-mail on Thursday.
"There is nothing to be afraid of as regards European education standards - they do not pose a threat but are rather a guarantee of your future. The same applies to the rule of law. As the least numerous people in Bosnia-Herzegovina, you have the opportunity to benefit more than anyone else from the unbiased enforcement of the rule of law. Beware of those who want to prevent that because in the future you will rely exactly on that principle," Ashdown said in his message to Bosnian Croats.
He assured Serb representatives that he had no intention of abolishing Republika Srpska.
"It is nobody's policy to abolish Republika Srpska, but Republika Srpska must respect international law and understand that it is not a state but part of a state," Ashdown said.
Addressing Bosniaks, he said that they would "have to accept compromise more than others if they want to have a state where they are the ones to be consulted most, but where others will be able to feel safe enough".
Ashdown voiced confidence that 2005 would be a year of more significant integration with NATO and European structures.
"When I arrived in Bosnia-Herzegovina, I said that I would measure my success by how close I am to the moment when Bosnia-Herzegovina would no longer need a High Representative of this type. This continues to be my goal and I believe that that moment is near, if we manage to join NATO and Europe," Ashdown added.
He said that 2004 was successful for Bosnia-Herzegovina, but added that even greater challenges lay ahead, announcing changes to the country's constitution.
"Most structures of authority should be decentralised wherever it is possible," the High Representative said, adding that he expected four federal ministries to be relocated to Mostar.