“My message is clear: we must accelerate the process because there is still a lot of work to do,” he told journalists on the sidelines of the UN conference in Paris' northern outskirts.
“Options for compromise need to be found as quickly as possible,” he added.
“Heads of state and government on Monday gave us an unambiguous mandate, and we must succeed.”
Since a high-profile opening by more than 150 world leaders on Monday, bureaucrats have been poring over a draft of the first pact to propose a global roster of carbon-curbing undertakings.
The goal is to limit warming to 2C (3.6 degrees Fahrenheit) over pre-Industrial Revolution levels.
The marathon conference is scheduled to close at 6 pm (1700 GMT) on December 11th – but the process is notorious for textual bickering and running over schedule.
Bureaucrats have been given an interim deadline of midday (1100 GMT) this Saturday to produce a blueprint, which will then be given to environment ministers to make the political decisions required for a deal.
A European negotiator earlier told AFP there was “growing frustration” with what he described as a “very slow” pace of work.
And Greenpeace campaigner Li Shuo, who has observer status in the talks, described the process as “quite messy”, with negotiations in “contact groups, spinoff groups, informal informals, huddles”.
“At some point, we definitely need to switch gear,” he said.
UN climate chief Christiana Figueres cautioned against despair.
“The text of the agreement will go through ups and downs, there will be many commas inserted and commas removed because that is the nature of this. It is a legally binding text and needs to be reviewed very, very carefully,” she said.