To save the British from what he thought was a disastrous action and to stop the war from a possible escalation, Canadian Secretary of State for External Affairs Lester B. Pearson proposed the creation of the first United Nations peacekeeping force to ensure access to the canal for all and an Israeli withdrawal from the Sinai Peninsula. On 4 November 1956, a majority at the United Nations voted for Pearson's peacekeeping resolution, which mandated the UN peacekeepers to stay in Sinai unless both Egypt and Israel agreed to their withdrawal. The United States backed this proposal by putting pressure on the British government through the selling of sterling, which would cause it to depreciate. Britain then called a ceasefire, and later agreed to withdraw its troops by the end of the year. Pearson was later awarded the Nobel Peace Prize. As a result of damage and ships sunk under orders from Nasser the canal was closed until April 1957, when it was cleared with UN assistance. A UN force (UNEF) was established to maintain the free navigability of the canal, and peace in the Sinai Peninsula.