BUDAPEST, May 7, 2018 (Reuters) - Hungary's President Janos Ader has asked Viktor Orban to form his new government and proposed on Monday that parliament should elect Orban prime minister for a new four-year term. Orban, 54, who was reelected for a third straight term in elections last month, told a news conference that his government's main task would be "to preserve Hungary's security and Christian culture". Parliament will hold its first session on Tuesday. Orban's right-wing nationalist Fidesz party holds 133 of 199 seats.