The EU called Thursday on India, Indonesia, Brazil and other major economies to immediately submit their emissions reductions targets ahead of the UN climate summit in Paris at year's end.

EU Climate and Energy Commissioner Miguel Arias Canete warned that the window of opportunity for 195 countries to agree a deal aimed at limiting the rise in global temperatures "is closing fast" and called for speeding up technical negotiations.

So far he said 56 countries representing 61 percent of global green-house gas emissions have handed in their reduction pledges, just over a quarter of the total countries.

"Key G20 countries such as Argentina, Brazil, India, Indonesia, Saudi Arabia, South Africa and Turkey must submit their intended contributions without delay," the Spanish commissioner told a press conference.

Underscoring the challenges ahead on global warming, US government scientists said Thursday that July was the hottest month in history, and the first seven months of the year were also the warmest since modern record-keeping began in 1880.

French President Francois Hollande warned that failing to reach a UN climate pact in Paris would be a "disaster".

In March, the European Union, the world's third biggest emitter, became one of the first blocs or countries to formally submit its pledge to the United Nations.

The second biggest polluter the United States and the number one emitter China have also submitted their pledges in the last few months.

Canete praised these contributions, also noting the efforts of "some of the most vulnerable countries from Africa, the Caribbean and the Pacific" to come up with proposals.

- Window of opportunity closing -

The failure of so many of the world's 20 biggest economies to submit their pledges makes it difficult to calculate the total cuts still needed to limit global warming to no more than two degrees Celsius (3.6 degrees Fahrenheit) over pre-industrial levels, Canete said.

The EU wants the two degree target embedded in a Paris agreement.

The calculation needs to be done quickly, he said, to "know where we stand" before the climate conference running from November 30 to December 11 in the French capital.

"The window of opportunity to keep the global rise in temperature to two degrees is closing fast," he warned.

Canete's hard-hitting remarks were the first time such a senior EU official had publicly named countries to come forward quickly with their emission reduction pledges.

EU sources told AFP the 28-nation EU already launched in March a campaign urging 60 countries to submit their pledges as soon as possible but analysts said the appeals fell on deaf ears despite the bloc's combined diplomatic heft.

- 'Painfully slow' talks -

He also said that while he sees the "political will to achieve an ambitious" agreement, "in the negotiating room progress has been painfully slow."

He added: "The technical negotiations must go faster."

He said an ambitious deal would be one that is legally "binding" and allows for a review every five years to see how well it is being implemented.

Canete told AFP later that "one of the most difficult questions that we have to settle" is over the opposition of the United States and many other countries to an internationally binding agreement.

"Until now no progress has been achieved," he said when asked whether the issue could block the negotiations.

Last October EU member states agreed to cut emissions by 40 percent by 2030 over a benchmark of 1990, a binding target that Canete hails as the world's "most ambitious".

By comparison, US President Barack Obama set a target for the United States to cut its overall emissions by 26-28 percent from 2005 levels by 2025.

The UN Paris conference will seek to crown a six-year effort by 195 nations with a post-2020 pact on curbing greenhouse gases blamed for climate change involving more drought, floods and rising seas.