There has been discussions among analysts about the possibility of re-equipping the Borei-class submarines with the more reliable liquid-propellant R-29RMU Sineva missiles. The Sineva is an upgrade of the R-29RM Shtil and entered service in 2007. According to "RIA Novosti" military analyst Ilya Kramnik, this would have been an attractive option, given that the less advanced Sineva missiles already have "virtually the same impressive specifications as the Trident II (D5) SLBMs wielded by the U.S. Navy and the Royal Navy." However, the work needed to redesign and modify the Borei-class submarines to carry Sinevas is regarded as too expensive.