More targets envisioned

Experts have also expressed high expectations about major economies unveiling more ambitious climate targets before or at the virtual summit.

According to a statement by the US government, by the time of the summit, the US will announce an ambitious 2030 emissions target as its new Nationally Determined Contribution for post-2020 climate action under the Paris Agreement.

Quoting unnamed sources, The Associated Press said in a report on Tuesday that Biden will pledge to cut US greenhouse gas emissions by at least half by 2030, which is nearly double the nation's previous commitment.

"While China announced an updated nationally determined contribution last December, the ball is now in the US court," said Zhang Jianyu, founder and chief representative of the Environmental Defense Fund's China program.

China announced late last year that it will lower its carbon dioxide emissions per unit of GDP by over 65 percent from the 2005 level and increase the share of non-fossil fuels in primary energy consumption to around 25 percent by 2030. The country will also increase the share of non-fossil fuels in primary energy consumption to around 25 percent.

The European Union also reached a tentative climate deal on Wednesday that is intended to make the bloc climate neutral by 2050.

"Our political commitment to becoming the first climate neutral continent by 2050 is now also a legal commitment. The climate law sets the EU on a green path for a generation," European Commission President Ursula von der Leyen said early on Wednesday.

Under the provisional deal reached after officials negotiated through the night, the EU will also commit itself to an intermediate target of cutting greenhouse gas emissions by at least 55 percent by 2030 compared with 1990 levels, AP reported.

On Tuesday, the UK government pledged to cut carbon emissions by more than three-quarters of their 1990 levels by 2035 while closing a loophole that had left much of the pollution from airplanes and ships out of the tally, according to AP.

On Wednesday, Russian President Vladimir Putin said that Russia's emissions of greenhouse gases should be less than the EU's over the next 30 years, but that it would be difficult to reach that goal given Russia's size, Reuters reported.