Kuwaiti Emir Sheikh Sabah's condition is improving as he receives treatment in the US, Prime Minister Sheikh Sabah Al Khalid Al Sabah has told the Cabinet. The monarch, 91, is undergoing treatment in the US to complete medical treatment after surgery in Kuwait for an unspecified condition on July 19. The emir was admitted to hospital the previous day for medical checks. During a cabinet session Monday, Sheikh Sabah Al Khalid said he received a call from the deputy head of the national guard reassuring him of the emir's health. He “assured the council of the health of the emir, God safeguard and care for him, who is witnessing noticeable improvement”. Sheikh Sabah left for the US 12 days ago aboard a US Air Force C-17 flying hospital, AP reported. US medical officers and Kuwaitis were aboard the flight for the 16-hour journey that briefly stopped at Germany’s Ramstein Air Base. The US has not officially said it flew the monarch, but a State Department official said they had “provided assistance to help with the emir’s treatment”, without giving specifics. Kuwait's state-run Kuna news agency said the country's ambassador to the US was at the airport for the plane’s arrival. Flight-tracking data showed the plane landing in Minnesota, near the flagship campus of the Mayo Clinic, one of the US’s best hospitals and one that has treated Sheikh Sabah in the past. The US military uses C-17s as airborne hospitals for medical evacuations. The aircraft have on-board oxygen and the same life-saving equipment found in hospital emergency rooms. The flights often include critical care air transport teams, with a specialist doctor, a nurse and a respiratory therapist. Sheikh Sabah has ruled Kuwait, one of the world's biggest oil exporters, since 2006. Last year he was admitted to hospital in the US while on an official visit, after what his office said was a health setback. Sheikh Sabah returned to Kuwait in October. Kuwaiti Parliament Speaker Marzouq Al Ghanim said last week that news about Sheikh Sabah’s health was "very reassuring". After a royal decree, Crown Prince Nawaf Al Ahmad Al Sabah has temporarily assumed some of the emir’s duties.