ROME — G20 negotiators worked through the night but failed to reach agreement on how to phrase the section of the leaders’ final communiqué on climate change, according to three Western diplomats with knowledge of the talks.

The precise text on combatting climate change, including proposals to eventually phase out the use of coal and scale up action during this decade, has been the most contentious aspect of this year’s G20 summit, and is also the most crucial given the imminent start of the COP26 climate conference in Scotland on Sunday.

Many of the G20 leaders are flying directly to Glasgow from Rome, and the statement by the world’s 20 leading economies was expected to set the tone for the much larger forum, which will be attended by nearly 200 countries.

“Leaders need to lead,” a U.K. diplomat said.

Two other diplomats cautioned that negotiations were still actively underway and the situation was in flux.

Jacopo Barigazzi contributed reporting.