Leading the U.N. push for parties in Ukraine to resolve the country's ongoing political crisis through peaceful dialogue, Secretary-General Ban Ki-moon on Monday said he was "deeply concerned and disappointed" that Sunday's Crimea secession referendum only will worsen an "already complex and tense situation." "The secretary-general continues to closely follow the situation in Ukraine," Ban spokesman Stephane Dujarric told reporters at U.N. headquarters in New York City, adding that since the start of the crisis, the U.N. chief has urged all parties to avoid "hasty steps" that could exacerbate tensions. "He encourages all parties to work for a solution that is guided by the principles of the United Nations Charter, including respecting Ukraine's unity and sovereignty," Dujarric said. Ban also condemned the violence that occurred over the weekend in eastern Ukraine and which resulted in injuries and deaths. "The secretary-general once again urges all parties to refrain from violence and to commit themselves to de-escalation and inclusive national dialogue in the pursuit of a political and diplomatic solution," Dujarric said. "A deterioration of the situation will have serious repercussions for the people of Ukraine, the region, and beyond." "Above all, the secretary-general urges all concerned to intensify their efforts and engage constructively toward a peaceful solution to this crisis, with the aspirations of all the people of Ukraine foremost in mind," Dujarric said.