LONDON (Reuters) - British foreign minister Boris Johnson said on Thursday he believed that Libya s plans to work toward elections in 2018 were probably  the right timescale . In July, rival leaders pledged in Paris to work towards elections in 2018 and a conditional ceasefire. U.N. Libya envoy Ghassan Salame said constitutional and electoral laws would have to be written to ensure any vote brought lasting change.  Would it be premature to hold the elections within a year? I happen to think that could be about the right timescale,  Johnson told a joint news conference with visiting U.S. Secretary of State Rex Tillerson.  It is very important however, that you don t do it too fast and that you get the political groundwork done first,  he added.  There has to be a constitution, there has to be an accepted basis for those elections to take place.  