LONDON — Syrian opposition leaders are set to unveil plans for a political transition ahead of a Friends of Syria meeting in London.

The High Negotiations Committee scheme is set to be made public Wednesday in a session at the International Institute for Strategic Studies. The goal is to end the long-running civil war inside Syria with a political settlement that could be implemented with international support.

Foreign ministers from the Friends of Syria group hosted by British Foreign Secretary Boris Johnson will meet later Wednesday to discuss ways to curtail the fighting, which has helped spawn a huge refugee crisis.

Previous international plans have failed to bring the fighting to an end.