The American leader refused to reaffirm his country's commitment to the accord at a G7 summit in Italy on Saturday.
He said he would make up his mind after returning to the US.
Mr Trump, who has called climate change a "hoax" on occasion, has reportedly indicated this is still his position to key members of his inner circle.
In 2015, nearly 200 countries agreed to the landmark accord, which aims to reduce global carbon emissions.
Responding to the reports, a top EU official said Europe was ready to assume leadership on combating climate change.
"If they decide to pull out it would be disappointing but I really do not think this would change the course of mankind," European Commission Vice-President Maros Sefcovic was quoted as saying by Reuters news agency.
"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."
German government spokeswoman Ulrike Demmer said: "Like you I've seen the reports but I don't have any information beyond that.
"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."
In the US, Ed Markey, a Democratic senator, tweeted: "Pulling out of #ParisAgreement is a massive moral, economic & leadership failure for Trump admin. Loss of business, jobs, & intl standing."
US President Donald Trump is poised to pull the country out of the Paris climate accord, US media report, quoting senior officials.