U.S. President Donald Trump has decided to withdraw from the Paris climate accord, the Axios news outlet reported Wednesday, citing two unidentified sources with direct knowledge of the decision.

Trump, who has previously called global warming a hoax, refused to endorse the landmark climate change accord at a summit of the G-7 group of leading industrial nations on Saturday, saying he needed more time to decide. He then tweeted that he would make an announcement this week.

Governments around the world expressed concern over the reports.

"Like you, I've seen the reports but I don't have any information beyond that," German government spokeswoman Ulrike Demmer told reporters.

"So I can only reiterate the well-known position that the German government unequivocally supports the Paris climate agreement and is campaigning for it to be quickly implemented and hopes the USA remains committed to this agreement," she added.

Finland's prime minister, Juha Sipila, told parliament on Wednesday that if the United States withdraws from the Paris climate deal, it would be a major reversal.

"If this is true, it is a big setback. Then, we must find partners to continue, because this work must not stop," Sipila said.

The decision also drew a reaction from the United Nations, with the organization's main Twitter page quoting Secretary-General Antonio Guterres as saying: "Climate change is undeniable. Climate change is unstoppable. Climate solutions provide opportunities that are unmatchable," according to The Associated Press.

However, the European Union stands ready to take on the mantle of leadership on this issue, according to the European Commission.

"If they decide to pull out it would be disappointing but I really do not think this would change the course of mankind," said European Commission Vice President Maros Sefcovic.

"There is a much stronger expectation from our partners across the world from Africa, Asia and China that Europe should assume leadership in this effort and we are ready to do that," Sefcovic added.

The decision to withdraw from the climate accord was influenced by a letter from 22 Republican U.S. senators, including Majority Leader Mitch McConnell, calling for an exit, Axios reported.

Former President Barack Obama, who helped broker the accord, praised the agreement during a trip to Europe this month.

The United States is the world's second-biggest carbon dioxide emitter behind China.

Supporters of the climate pact are concerned that a U.S. exit could lead other nations to weaken their commitments or also withdraw, softening an accord that scientists have said is critical to avoiding the worst impacts of climate change.

Canada, the European Union, and China have said they will honor their commitments to the accord even if the United States withdraws. A source told Reuters that India had also indicated it would stick by the deal.

Trump had vowed during his campaign to "cancel" the Paris deal within 100 days of becoming president, as part of an effort to bolster U.S. oil and coal industries. That promise helped rally supporters sharing his skepticism of global efforts to police U.S. carbon emissions.

After taking office, however, Trump faced pressure to stay in the deal from investors, international powers and business leaders, including some in the coal industry. He also had to navigate a split among his advisors on the issue.

-- CNBC.com contributed to this report.