NEW DELHI (Reuters) - India, the world's third largest emitter of greenhouse gases, formally joined the Paris agreement on tackling climate change on Sunday, the United Nations said, taking the global pact a step closer to its enactment.

The deal, agreed by nearly 200 countries in Paris last December, aims to slash greenhouse gas emissions by shifting away from fossil fuels to limit global warming to "well below"two degrees Celsius compared to pre-industrial times.

But it needs to be formally ratified by countries representing at least 55 per cent of global carbon dioxide emissions.

"The Secretary-General calls on all Parties to accelerate their domestic procedures in order to join the agreement as soon as possible this year," said a spokesman for the UN Secretary-General in a statement.

Next week the European Union is expected to complete the joint ratification of the climate pact, which will be a major milestone as it would take approvals past the 55 per cent mark and put the deal into effect ahead of the next round of climate talks in November, in Morocco.

The Paris agreement received a boost last month after the United States and China, the world's two biggest emitters, submitted their approvals to the United Nations.

Concerns about the participation of the United States loom over the deal but cementing the accord before the US presidential election on Nov 8 would make it harder to challenge if Republican Donald Trump, who has opposed it, beats Democrat Hillary Clinton, a strong supporter.

President Obama welcomed India's ratification in a tweet, saying Prime Minister Narendra Modi and the country was carrying on the legacy of Mahatma Gandhi and his belief "in a world worthy of our children".

India had called for more work on the agreement ahead of its ratification on Sunday, with its environment ministry saying the Paris agreement laid a "broad framework" but detailed guidelines and rules were needed for it to become operational.

The ministry also criticised developed countries, saying their populations "live extravagant lifestyles with a high carbon footprint".

It said it was "very crucial" to advance key issues, including those related to finance and technology transfer, at the meeting in Marrakech next month, where India also plans to urge developed countries to do more.

"At Morocco India will insist on a concrete roadmap from developed countries," the ministry said.