White House climate adviser Gina McCarthy is planning to resign, likely capping off a tenure marked by ambitious emissions targets, but a failure to secure major US carbon-cutting legislation, according to two sources familiar with the discussions.

McCarthy, 67, had planned to stay in the White House for about a year to assist federal agencies in implementing Joe Biden's ambitious climate legislation, but those efforts were stymied by intraparty opposition from key Democratic senators, including Joe Manchin.

Furthermore, McCarthy has already postponed her departure, telling Reuters that she plans to leave as soon as next month.

On his account, White House spokesperson Vedant Patel said on Thursday, “This is not true and there are no such plans underway and no personnel announcements to make.”

“Gina and her entire team continue to be laser-focused on delivering on President Biden’s clean energy agenda,” he added in an email.

McCarthy told confidantes that she planned to leave her job in the coming months, according to multiple news outlets, including the New York Times and the Washington Post, with the Times reporting that she was "frustrated by the slow pace of climate progress."

According to a December Politico poll, 80 percent of Americans who identified as left-leaning believe the Biden administration is doing too little to address climate change. McCarthy responded publicly to that sentiment in February, according to Politico, saying, "We understand people's frustration. Would we all like to be running faster and faster? Yes, we would."

McCarthy, a former EPA administrator during the Obama administration, was appointed by Biden to a new position leading domestic climate policy coordination at the White House. She is Biden's domestic counterpart to John Kerry, whom he appointed as his special international envoy on climate change.

According to the Washington Post, her deputy, Ali Zaidi, who worked as a climate policy adviser in the Obama administration, is seen as her likely replacement.

Biden took office with a bold climate agenda, including a $555 billion plan to transition to cleaner energy in all aspects of American life. McCarthy, a regulatory expert, was going to be tasked with implementing the plan across multiple agencies before those policies stalled.

The US president promised to wean the country off fossil fuels but now finds himself looking for ways to increase the global supply of oil and other carbon-rich energy products in the face of war in Ukraine and high gas prices, which advisers say are harming his standing with voters.

McCarthy's position was a key demand of the Democratic Party's liberal wing, and it demonstrated Biden's dedication to the cause. The environmental community may interpret her absence as a retreat.

It is worth noting that following his victory in the elections in November last year, Joe Biden had made a vow on the matter of environmental protection that he will focus more on clean energy and ban the leasing of federal lands for coal and natural gas mining. He had also pledged to decrease methane emissions resulting from oil and gas production, not to mention his plan to establish a division of environmental and climate justice within the Department of Justice, further enhancing law enforcement against polluters.