COPENHAGEN - Countries fired the first shots in three-way battle on climate change in Copenhagen on Friday, wrangling over a seven-page document proposed as the blueprint of a historic pact.

The world's No. 1 and 2 polluters, China and the United States, laid down markers in what promises to be a fiery week-long haggle, culminating in a world summit on December 18.

The text, seen by AFP, sees targets of limiting global warming to 1.5 or 2.0 degrees Celsius (2.7 or 3.6 degrees Fahrenheit).

It also foresees a second commitment period under the Kyoto Protocol boycotted by the United States.

But it is vague on climate funding, does not spell out a deadline for concluding a legally-binding treaty, and does not include a year by which emissions must peak -- all key negotiation issues.

The document will be debated by environment ministers from around the world, with the goal of sealing an endorsement at a summit on December 18 to be attended by more than 110 leaders.

Kim Carstensen of WWF was upbeat.

"The text provides a basis to make the right political decisions. It contains many gaps, exposes rifts, but also clearly shows that an agreement is possible."

If all goes well, a political agreement in Copenhagen would be followed by meetings in 2010 under the 194-nation UN Framework Convention on Climate Change (UNFCCC) to flesh out key details.

The global pact would take effect from 2013, after current pledges expire under the UNFCCC's Kyoto Protocol.

The proposed draft, put forward by one of the two negotiating tracks in the 12-day talks in Copenhagen, contains many gaps and brackets, denoting discord.

On the question of a target for warming, it reads:

"Parties shall cooperate to avoid dangerous climate change, in keeping with the ultimate objective of the Convention, recognizing [the broad scientific view] that the increase in global average temperature above pre-industrial levels ought not to exceed [2 C] [1.5 C]."

The lower temperature is embraced by small island states and many African nations badly threatened by climate change, while the higher target has been supported by rich nations and emerging giants such as China, India and Brazil.

The draft leaves open three possible targets for the overall reduction of global carbon emissions by 2020, compared with 1990 levels: by 50 percent, by 80 percent and by 95 percent.

Industrialised countries favour the 50 percent goal, while major emerging economies led by China have balked at any such target unless rich countries assume the near totality of the burden.

For rich countries, which acknowledge their historical responsibility for global warming, the bracketed options for CO2 cuts by 2050 range from 75-85 percent, "at least 80-95 percent", and "more than 95 percent", all measured against the same 1990 benchmark.

The text stands by a second, seven-year commitment period of the UNFCCC's Kyoto Protocol, the pact shunned by the United States, which runs out at the end of 2012.

US emissions targets -- and voluntary actions by developing countries -- would be included in an "appendix" under the UNFCCC.

A draft text in an parallel negotiation pool -- covering only parties to the Kyoto Protocol -- calls for rich-country commitments of greenhouse-gas cuts of 30 to 40 percent by 2020 compared to 1990.

On the key question of funds to help poorer countries adopt lower carbon energy and shore up their defences against climate change, the draft text is vague.

"Scaled-up, predictable, new and additional, and adequate funding shall be provided," it says, but does not give figures.

The document allows for "fast-start" financing for three years starting in 2010 to help poor nations cope with warming, but does not specify an amount.

Rich countries have proposed 10 billion dollars per year during this period.

In Brussels, European Union (EU) agreed to give 7.2 billion euros (10.8 billion dollars) over three years.

In an early sign of the tensions ahead, China demanded that rich nations spell out long-term commitments on funding, while the United States said the text on emissions curbs meant China and other emerging giants would not be required to pull their weight.

"The United States is not going to do a deal without major developing countries stepping up," said chief US negotiator Todd Stern.

"The draft says that developed countries have legally binding commitments to tackle (...) but does not in any sense call on major developing countries to," he said.

"So we don't think that that particular section of the text is an acceptable starting point negociation with respect to this issue."