The climate deal President Obama wants to sign onto in Paris is legally questionable and functionally lopsided, said the head of the largest business lobby in the U.S.

Tom Donohue, the president of the U.S. Chamber of Commerce, on Monday outlined a host of flaws with the president's climate change plan as Obama joins foreign leaders in Paris this week to pledge U.S. emission cuts under a United Nations climate change deal being negotiated.

"The president has pledged that the United States will reduce its greenhouse gas emissions by up to 28 percent by 2025," Donohue said. "While the administration has rammed through a series of regulations to achieve its goal, about 45 percent of the emission cuts are still unaccounted for. Moreover, the centerpiece of the U.S. pledge, the Clean Power Plan, stands in serious legal jeopardy."

Donohue's group is suing the administration, along with 27 states, over the Clean Power Plan, which they argue is unconstitutional and not justified by current law. The Clean Power Plan calls on states to reduce emissions a third by 2030.

Many scientists say the greenhouse gas emissions that the president seeks to cut are causing the Earth's climate to warm, resulting in more severe weather, floods, droughts, and economic and social unrest. Donohue argues that the president's plan to solve those problems will make it more expensive for people to live and support their families.

But the deal the president is seeking to agree to is too "lopsided" to do much good on the emissions front, while creating uncertainty for the U.S. economy, Donohue said. The U.N. deal being hashed out beginning Monday makes the U.S., Europe and other developed countries do the heavy lifting on emissions reductions, while the developing countries are allowed to continue to emit to support their economies, he said.

"The United States, Europe, Japan, and a few other developed nations have pledged significant reductions — even though together they make up less than 30 percent of global emissions," he said. "But many developing nations are more concerned with growing their economies than cutting emissions and have made only modest pledges.

"Even if every nation reaches its reduction goal, global emissions will still rise by 18 percent between 2010 and 2030."

At the same time, the U.S. and other advanced nations will have to "pony up" large sums of cash to help developing nations adapt to changes stemming from global warming. The funds are expected to reach $100 billion a year by 2020 to create what is called a Green Climate Fund. But many developing nations argue the amount should be increased.

"China, for example, has proposed that developed countries kick in 1 percent of their annual [gross domestic product] starting in 2020," Donohue said. "In 2014, that would have been $170 billion from the U.S. [alone]."

"Other financing suggestions are equally extravagant," he said. "And the president has already promised an initial contribution of $3 billion."

Republicans have vowed not to appropriate funds to meet Obama's climate fund obligations, while many nations on Monday announced increased pledges to the fund. For example, Canada committed $30 million to support actions that would help the poorest nations.

Canada's pledge adds to the $2.65 billion "over the next five years to support developing countries' transition to low-carbon economies that are both greener and more climate resilient. This is the most significant Canadian climate finance contribution ever," a statement from the foreign ministry read.