The United States is expected to announce on Monday that all buyers of Iranian oil will have to end their imports shortly or face sanctions, a source familiar with the situation told Reuters, triggering about a 3 percent rise in crude prices.U.S. President Donald Trump has been clear to his national security team over the last few weeks that he wants the waivers to end, and National Security Adviser John Bolton has been working the issue within the administration.In November, the U.S. reimposed sanctions on exports of Iranian oil after President Trump unilaterally pulled out of a 2015 nuclear accord between Iran and six world powers.Global benchmark Brent crude oil futures rose by as much as 3.2 percent to $74.30 a barrel, the highest since Nov. 1......