SAN SALVADOR, Dec 10 (Reuters) - U.S. authorities are preparing criminal charges against El Salvador"s deputy justice minister Osiris Luna and another senior official, accusing them of negotiating a secret truce with gangs, two sources said, amid rising tensions between Washington and President Nayib Bukele"s government. According to the sources, the indictments are being prepared by a Department of Justice (DOJ) taskforce against Luna and Carlos Marroquin, a close Bukele ally who heads a Salvadoran government social welfare agency. The U.S. Treasury imposed sanctions on Luna and Marroquin on Wednesday, accusing them of cutting a deal with the Mara Salvatrucha (MS-13) and Barrio 18 gangs, in which the gangs would reduce violence in El Salvador and provide political backing in return for money and easier prison conditions. Bukele has repeatedly denied his government negotiated any truce and denounced the sanctions. The two sources familiar with the matter told Reuters the DOJ was now preparing criminal charges against Luna and Marroquin. Luna, a member of Bukele"s cabinet who is also in charge of El Salvador"s prison system, and Marroquin did not respond to multiple requests for comment. The DOJ declined to comment. The investigation is being handled by the Joint Task Force Vulcan (JTFV), a DOJ unit set up in 2019 to coordinate efforts by U.S. law enforcement agencies to dismantle MS-13, which has made inroads in U.S. cities and prisons, both sources said. U.S. officials say the gangs have ordered murders on U.S. soil from inside prisons in El Salvador. The U.S. government claims broad authority to prosecute for a wide range of crimes committed abroad, including for acts committed by or against American citizens. The task force has indicted several MS-13 leaders on terrorism charges in the Eastern District of New York. El Salvador classifies MS-13 as a terrorist organization and U.S. prosecutors have accused some of the group"s leaders of terrorist acts. While the timeline has not been finalized, the indictments are expected in coming months, said the sources, who sought anonymity as they are not authorized to publicly speak about the planned indictments. The U.S. Federal Bureau of Investigation (FBI) was involved in the probe, said one of the sources. The FBI did not respond to requests for comment. The two sources said the exact charges have not been finalized. The second source said they were likely to focus on corrupt practices and consorting with groups responsible for violent crimes. Building on Wednesday"s Treasury sanctions, the U.S. State Department on Thursday imposed a new set of penalties on Luna and Marroquin for "misappropriating public funds." The sanctions and the indictments being drafted are likely to further strain relations between Bukele and Washington, where the Salvadoran leader is seen as an increasingly authoritarian figure. Bukele on Thursday called the allegations "absurd." "It"s clear that the United States" government does not accept collaboration, friendship or alliances," said Bukele, a former mayor of the capital, San Salvador. "It"s absolute submission or nothing." URBAN CONTROL U.S. authorities also discovered that the MS-13 gang had put out a hit on an FBI agent when they intercepted a small piece of paper, known as a "wila," that the gangs use to pass on coded messages to their members outside prisons. The agent fled El Salvador with his family, according to the first source. Successive Salvadoran presidents have wrestled with how to curtail MS-13 and Barrio 18"s control over urban areas, where violence and extortion have spurred waves of emigration to the United States. Bukele was a staunch critic of a 2012 clandestine accord between the former government and gang leaders that collapsed two years later, resulting in a sharp increase in the country"s murder rate and leading to the arrest of several government officials. Rumors of a fresh accord swirled after the murder rate tumbled about 50% in the year after Bukele took office in June 2019. Homicides dropped to 17 murders per 100,000 people in 2021, down from 51 in 2018, according to the National Police. Bukele has credited the drop in homicides to his policies. In September 2020, newspaper El Faro, citing internal government documents, reported that Luna and Marroquin offered better prison conditions to gang members in exchange for reduced homicide rates and electoral support for Bukele"s party.