FLINT, Mich. — Sipping filtered city water to show it’s again drinkable, President Barack Obama promised Wednesday to ride herd on leaders at all levels of government until every drop of water flowing into homes in Flint, Michigan, is safe to use.

He also promised that the aging pipes that contaminated the water with lead will be replaced, but cautioned that the project will take time. Obama said he wanted to use the crisis to make long-term improvements to the city, where more than 40 percent of residents live in poverty.

“It’s not going to happen overnight, but we have to get started,” Obama told hundreds of people gathered in a high school gymnasium. Obama spoke after he was briefed on the federal response to the water contamination and had met privately with nine residents.