(Reuters) - 
Almost 200 nations kept a plan to reach a new U.N. climate pact in 2015 
alive on Saturday when rich and poor countries reached a compromise on 
sharing out the efforts needed to slow global warming.
A two-week negotiation in 
Warsaw had been due to end on Friday, but was blocked over a timetable 
for the first U.N. climate accord that would set greenhouse gas 
emissions requirements for all nations. The pact is due to be agreed in 
2015 and come into force after 2020.
Negotiators
 finally agreed that all countries should work to curb emissions - a 
process described in the jargon as "intended nationally determined 
contributions" - as soon as possible and ideally by the first quarter of
 2015.
The agreement ended deadlock
 between rich and poor about sharing out the burden of limiting 
emissions blamed for causing more heatwaves, floods, droughts and rising
 sea levels.
Under the last climate
 pact, the Kyoto Protocol, only the most developed countries were 
required to limit their emissions - one of the main reasons the United 
States refused to accept it, saying rapidly growing economies like China
 and India must also take part.
"Just
 in the nick of time, the negotiators in Warsaw delivered enough to keep
 the process moving," said Jennifer Morgan of the World Resources 
Institute think-tank.
China had 
insisted that developing nations should announce deep cuts in emissions 
while allowing emerging economies room to burn more fossil fuels to help
 end poverty.
But the United States
 noted that all nations agreed in 2012 that the 2015 deal would be 
"applicable to all" and accused emerging nations of harping back to 
previous deals.
"I feel like I am going into a time warp. That is folly," said Todd Stern, the U.S. special envoy for climate change.
Developed nations had wanted all to take on "commitments", not the weaker-sounding "contributions" that they settled for.
CLIMATE AID
Before
 Saturday, the only concrete measure to have emerged after two weeks was
 an agreement on new rules to protect tropical forests, which soak up 
carbon dioxide as they grow.
During
 the Warsaw meeting, no major nation offered tougher action to slow 
rising world greenhouse gas emissions and Japan backtracked from its 
carbon goals for 2020, after shuttering its nuclear industry after the 
Fukushima disaster.
Even after 
breaking the deadlock over which countries should tackle emissions, 
talks continued on another issue that has divided rich and poor: the aid
 that developed countries pay to developing ones to help them curb 
emissions and cope with to the impacts of climate change.
Developed
 nations, which promised in 2009 to raise aid to $100 billion a year 
after 2020 from $10 billion a year in 2010-12, have resisted calls to 
set targets for 2013-19.
A draft 
text merely urged developed nations, which have been more focused on 
spurring economic growth than on fixing climate change, to set 
"increasing levels" of aid.
The 
talks have also proposed a "Warsaw Mechanism" which would provide 
expertise, and possibly aid, to help developing nations cope with loss 
and damage from extreme events such as heatwaves, droughts and floods, 
and creeping threats such as rising sea levels and desertification.
Developing
 nations have insisted on a "mechanism" - to show it was separate from 
existing structures - even though rich countries say that it will not 
get new funds beyond the planned $100 billion a year from 2020.