Rebels sell oil San Antonio-based Tesoro told Reuters on Wednesday it bought the Libyan rebel crude to process in its Hawaii refinery. The deal was first agreed upon in late April, company spokesman Mike Marcy said. "We purchased a cargo of Libyan crude that was available at the time," he said in an email. Swiss oil trading firm Vitol SA, which loaded the crude onto a tanker in Libya in early April, acted as middleman in the transaction, trading sources said. While Vitol marketed the crude, Tesoro's purchase of the cargo marked the first transaction involving Libya's eastern rebels and a major foreign commercial user of oil. "It's an important precedent because it proves the rebels can find international buyers for their oil," a source at a major oil tanker operator told Reuters, requesting anonymity.