WARSAW, Poland (AP) — Poland's Prime Minister Mateusz Morawiecki flew Tuesday to the United States for meetings aimed at strengthening the economic and defense cooperation of the two nations.

Morawiecki is due to meet with Vice President Kamala Harris on Tuesday at the White House. He is also scheduled to have meetings with the representatives of American defense companies during his three-day visit.

“I am flying to the United States to strengthen the alliance with our most powerful ally, with a country that guarantees security in Europe, that especially guarantees security in our part of Europe,” Morawiecki said.

Following Russia's full-scale invasion of Ukraine last year, the United States increased its military presence in Poland — a nation on NATO's eastern flank that borders Ukraine — and has used Poland as a transit country for military and humanitarian aid going into Ukraine.

Poland is also a major donor of aid to Ukraine, and has been ordering tanks and other modern military equipment, mostly from U.S. and South Korean producers, to strengthen its own forces and replace some older equipment sent to Ukraine.

As Europe seeks to gain energy independence, Poland is also planning to build nuclear power plants, and has chosen the U.S. government and Westinghouse as its partners for its first plant.

Before departing Warsaw early Tuesday, Morawiecki told reporters at the airport that Polish-American relations “have not been so good for a long time, and perhaps they have never been so strong.”

Morawiecki's visit follows two visits to Poland by U.S. President Joe Biden since Russia invaded Ukraine in February 2022.

The prime minister said Poland’s alliance with the U.S. is “an absolute foundation of our security.”

“It is based on two pillars: economic and defense cooperation. I am going to the U.S. to strengthen both of these pillars,” he said.