President Donald Trump on May 8 called for a "30-day unconditional ceasefire" between Ukraine and Russia.Yet, recent months have seen a series of failed peace talks and ceasefires, including one initially brokered by the U.S. in March. While Ukraine immediately agreed to the ceasefire, Russia repeatedly violated it.Washington and its partners are considering additional sanctions if the parties do not observe a ceasefire, with political and technical negotiations between Europe and the U.S. intensifying since last week, Reuters' source said."We felt in the discussions with the Americans a certain irritation towards the Russian posture, the lack of reactivity and seriousness in its responses to what was proposed before," the source told Reuters. "The decision is practically taken."Nearly two months ago, Ukraine accepted a U.S.