PARIS • Four months after settling on a plan to stave off calamitous global warming, more than 160 nations gather in New York tomorrow to ink the pact whose execution demands a radical overhaul of the global economy.

After the champagne moment when the world community sealed the hard-fought agreement in Paris on Dec 12, signing the document is an important step. The next, and final, procedural phase will be ratification by individual governments.

Only when 55 countries responsible for 55 per cent of global greenhouse gases have done so can the agreement enter into force.

A total of 163 countries have said they will attend the high-level signing ceremony hosted by United Nations chief Ban Ki Moon. About 60 heads of state and government will put pen to paper - including France's Francois Hollande and Canada's Justin Trudeau.

The United States and China - jointly responsible for 40 per cent of greenhouse gases - will not be represented at the highest level, but are sending Secretary of State John Kerry and Vice-Premier Zhang Gaoli respectively.

With so many countries present, "we should set a record for the signing of an international accord", French Environment Minister Segolene Royal, who presides over the climate forum, predicted before departing for New York. "It is clear that decision-makers have taken the urgency of the climate threat to heart. It is a very good sign."

Countries that do not sign the document tomorrow can do so in the year that follows. The agreement sets out broad lines of attack against climate change.

It defines the goal of limiting global warming to "well below" 2 deg C to 1.5 deg C if possible. It does not prescribe deadlines or targets for curbing planet-warming greenhouse gas emissions: These are described in further detail in non-binding pledges countries filed to shore up the pact.

AGENCE FRANCE-PRESSE