China must make significant investments now to meet the targets of last week's agreement with the United States on greenhouse gas emissions, a senior US official said Monday, predicting a big impact on its economy.

The agreement announced in Beijing by Chinese President Xi Jinping and US President Barack Obama has come under fire from Republicans as allowing China to do nothing for 16 years, even as US companies labor under mounting regulations.

But Gina McCarthy, the head of the US Environmental Protection Agency, said China will have to make profound changes in order to meet its commitments under the bilateral agreement.

China, the world's top polluter, agreed for the first time to slow the growth of its greenhouse gas emissions and ultimately reverse them, with emissions peaking "around 2030."

McCarthy said it represented "a big change that requires a lot of action now to turn this large an economy around. And that can't be done on a dime but it needs to get going right away."

"It is clearly a signal that they need to make significant economic changes in the structure of how they look at their economy, and it will require significant investment in zero carbon technologies, or low carbon technologies.

"It is going to resolve in the need for them to make an immediate shift in how they're looking at continuing to grow the economy," she said.

According to McCarthy, the bilateral agreement should contribute to a future global accord on climate change at a conference in Paris at the end of 2015.

But the legal form such an accord would take, whether a treaty or some other type of document, has not been defined yet, she said.

"As far as I know there've been no decisions made, and probably won't be until Paris on how you capture this international agreement, in what type of forum, and that impacts in what way it becomes enforceable or legally binding," she said.

Obama committed the United States in Beijing to reducing its greenhouse gas emissions between 26 to 28 percent by 2025, from 2005 levels, infuriating Republicans, who will control both chambers of Congress from January.

While Obama aims to implement climate actions through regulatory agencies like the EPA, Republicans want to pass laws aimed at counteracting them.