FILE PHOTO: Former Malaysian Prime Minister Mahathir Mohamad arrives to visit jailed opposition leader Anwar Ibrahim, who is recuperating from surgery, at Cheras Rehabilitation Hospital in Kuala Lumpur, Malaysia January 10, 2018. Prime Minister Mahathir Mohamad has submitted a letter of resignation to Malaysia's king, his office said on Monday, amid talk of forming a new governing coalition. REUTERS/Lai Seng Sin/File Photo

FILE PHOTO: Former Malaysian Prime Minister Mahathir Mohamad attends a meeting of political and civil leaders looking to change the government in Kuala Lumpur, Malaysia, March 27, 2016. The fate of Malaysia's ruling coalition had been in doubt after surprise weekend talks between it and opposition groups on forming a new government that would exclude Mahathir's anointed successor Anwar Ibrahim. REUTERS/Olivia Harris/File Photo

FILE PHOTO: Malaysian Prime Minister Mahathir Mohamad (L) chats with Deputy Prime Minister Anwar Ibrahim during a function in Kuala Lumpur, May 9, 1997. "The letter has been sent to His Royal Highness the King at 1 p.m.," Mahathir's office said in a statement. It was not immediately clear if Mahathir could form another government with the support of other parties, but his party, Bersatu, has also quit the ruling coalition, its president, Malaysian home minister Muhyiddin Yassin said on Facebook. REUTERS/David Loh/File Photo

FILE PHOTO: Malaysia's Prime Minister Mahathir Mohamad (R) chats with deputy premier Anwar Ibrahim, who is also the finance minister, in Kuala Lumpur, May 11, 1997. On Sunday, Anwar had accused Mahathir's party and "traitors" in his own party of plotting to form a new government with the United Malays National Organisation (UMNO), the former ruling party ousted in 2018 amid graft accusations. REUTERS/Stringer/File Photo

FILE PHOTO: Malaysian Prime Minister Mahathir Mohamad (2nd R) cuts a cake with help from his wife Siti Hasmah (2nd L), his deputy Anwar Ibrahim (L) and Anwar's wife Wan Azizah during UMNO's general assembly in Kuala Lumpur, Sepetember 7, 1997. Sources said Mahathir's party and a faction in Anwar's party met officials from UMNO and Islamist party PAS in efforts to form a new coalition and possibly back Mahathir to serve out a full five-year term as prime minister. REUTERS/Stringer/File Photo

FILE PHOTO: Malaysian Prime Minister Mahathir Mohamad gestures to his well-wishers before leaving a mosque after Friday prayers in Putrajaya near Kuala Lumpur October 31, 2003. The tussle between old rivals Mahathir, 94, and Anwar, 72, has shaped Malaysian politics for decades and tension has persisted, despite their alliance to win 2018 elections based on a promise that Mahathir would one day cede power to Anwar. REUTERS/Bazuki Muhammad/File Photo