United States Secretary of State Marco Rubio stated that Russia and Ukraine need to submit "concrete proposals" for ending the conflict, or Washington will step back as a mediator, US Department of State spokesperson Tammy Bruce revealed on Tuesday. "We are now at a time when concrete proposals need to be delivered by the two parties on how to end this conflict. How we proceed from here is a decision that belongs now to the [US] president [Donald Trump]. If there is no progress, we will step back as mediators," Rubio said, according to a readout by Bruce during a...