President Trump will face pressure on climate change and migration as he begins his first G7 summit in Italy on Friday, which will also have a heavy focus on terrorism.

Trump's pending decision on whether the United States will remain in the Paris Climate Accord is hanging over the summit, as the White House has said Trump won't announce his decision until after the gathering.

"He wants to do the right thing for the environment," National Economic Council Director Gary Cohn told reporters aboard Air Force One on Thursday. "He cares about the environment. But he also cares very much about creating jobs for American workers. He wants to hear what the Europeans have to say about that."

The other G7 countries support the Paris Climate Accord, which Trump campaigned against in the presidential race. He now says he hasn't made up his mind.

Trump on Thursday met in Brussels with French President Emmanuel Macron, who aides said is pushing for Trump not to withdraw from the pact.

Trump is also facing pressure back home. More than 20 Republican senators, including Senate Majority Leader Mitch McConnell, sent a letter Thursday to Trump asking him to leave the agreement, arguing it would subject the country to a "significant litigation risk" and make it more difficult to rescind the Clean Power Plan.

"Accordingly, we strongly encourage you to make a clean break from the Paris Agreement," the letter stated.

Former President Barack Obama committed the United States in 2015 to the accord, which aims to prevent global warming and lower greenhouse gas emissions in the United States.

Trump is in Sicily for two days of G7 meetings. The G7 is made up of Canada, France, Germany, Italy, Japan, the United Kingdom and the United States. It represents almost half of the world's GDP.

Cohn said the first session on Friday will be about foreign policy, the role of the G7, terrorism and the situation in Syria. Later in the day, participants are expected to discuss Libya, North Korea, Afghanistan, Pakistan and cybersecurity, trade, climate and energy, he said.

The president is also expected to meet Friday with Italian Prime Minister Paolo Gentiloni, who has pressed the president to allow more migrants to come to the United States.

"Italy's the host country ... They're going to talk about migration, what's going on from Libya to Europe, what's going on in other parts of Europe and the migration from Italy up to the north," Cohn said. "Every country in Europe has a migration issue. They have an employment issue."

Secretary of State Rex Tillerson told reporters Wednesday Trump will talk about how "these trade unbalances exist" with other countries.

"I don't think you can expect any trade agreement. What there will be is a very frank discussion and exchange on why these trade unbalances exist," Tillerson said. "Some of it is structural; some of it is fiscal."

Cohn predicted trade is "going to be a big topic."

"We are going to continue to fight for what we believe is right, which is free, open and fair trade, which the president has been very clear on what that means," he said. "We will have a very robust discussion on trade, and we will be talking about what free and open means."

Trump, who has been on his first foreign trip as president, has visited Saudi Arabia, Israel, Rome and Brussels over the last week. The trip has not been particularly contentious so far, though Trump had strong words for NATO member countries in a speech Thursday,

The president complained of "chronic underpayments" and told NATO members, including those who will be at the G7 summit, that they must "contribute their fair share" so that the alliance can focus on ways to fight terrorism and deal with immigration crises.

"The NATO of the future must include a great focus on terrorism and immigration, as well as threats from Russia and our NATO's eastern and southern borders," Trump said at NATO headquarters in Brussels.

Trump, referencing this week's bombing of a concert in Manchester, England, has frequently talked on the trip about Islamic terrorism, an expected topic at the G7.

"A lot is going to come up on terrorism," Cohn said. "Terrorism is going to be a very big topic. It's going to lead off."