Temperature profiles and effluent concentrations were measured during combustion of aqueous urea and ammonium nitrate at pressures of 1-15 MPa. Pollutant levels decreased, while the combustion temperature showed a non-monotonic change with increasing pressure. Experimental temperature profiles were applied in kinetic gas-phase simulations, and resulting species concentrations were in good agreement with experimental values. Sensitivity analyses indicated the kinetic parameters of isocyanic acid hydrolysis are the main source of uncertainty, possibly leading to the lower agreement observed for experimental and simulation carbon species. Rate of production analyses indicated that isocyanic acid is mainly consumed by hydrolysis to carbon dioxide, while nitric acid reacts with nitrous acid to produce water. Ammonia exhibited two channels of decomposition, reacting with either hydroxyl or nitrogen dioxide to form amidogen and either water or nitrous acid, respectively. Nitrogen was mainly formed by the three-body reaction of diazenyl. As pressure increased, the aforementioned pathways became increasingly dominant.