President Joe Biden says the U.S. is ramping up vaccine deliveries to hard-pressed states over the next three weeks and expects to provide enough doses to vaccinate 300 million Americans by the end of the summer or early fall. Biden is calling the push a “wartime effort.” He said Tuesday that his administration is working to buy an additional 100 million doses of each of the two approved coronavirus vaccines. And he acknowledged that states in recent weeks have been left guessing how much vaccine they will have from one week to the next. He called that “unacceptable” and said “lives are at stake.”