Prompted by Russian aggression, the E.U. and NATO vow new cooperation.

BRUSSELS — NATO and the European Union, in their first joint declaration on security cooperation since the Russian invasion of Ukraine, underscored on Tuesday the continuing importance of the trans-Atlantic relationship, playing down calls from Paris for more European military independence.

Led by the United States, “NATO remains the foundation of collective defense for its allies and essential for Euro Atlantic security,” the declaration states. While the nations of the European Union should spend more and more cooperatively on military matters and build stronger armies, the declaration said, European efforts should correspond to NATO’s strategy and not be in competition with it.

“We recognize the value of a stronger and more capable European defense that contributes positively to global and trans-Atlantic security and is complementary to, and interoperable with NATO,” the declaration said.

In a joint news conference after the signing, the European Commission president, Ursula von der Leyen; the president of the European Council, Charles Michel; and the secretary-general of NATO, Jens Stoltenberg, praised the new language of cooperation between the two organizations, spurred by Russia’s attack on European security and international law.

“We must continue to strengthen the partnership between NATO and the European Union,” Mr. Stoltenberg said. “And we must further strengthen our support to Ukraine.”

Mr. Stoltenberg said that after earlier joint declarations in 2016 and 2018, “we are determined to take the partnership between NATO and the European Union to the next level,” to address growing geostrategic competition, including from China.

Mr. Michel said the European Union had a new commitment to improve its military capacity in cooperation with NATO, as well as its resilience in areas like energy, disinformation and raw materials. The European Union is accelerating its enlargement and waking up to the threat of China, he said. “Strong allies make strong alliances,” he said.

Ms. von der Leyen echoed these sentiments. “We know that we have to strengthen and now deepen this more-than-20-year-old partnership, because Europe security is challenged and it is under threat,” including from China, she said. She listed four areas for enhanced cooperation with NATO: the threats of hybrid and cyberwarfare and terrorism; climate change; emerging and disruptive technologies; and resilience regarding critical imports and vital infrastructure, like pipelines.

Negotiations on the joint declaration have been lengthy and difficult, with sensitive issues ranging from European strategic autonomy to language about China. China is seen by the United States as a rival and strategic competitor but by Europe as more of a distant, troubling trade partner with unclear military ambitions outside Asia.

The two European officials, Ms. von der Leyen and Mr. Michel, have defended the idea of a broader strategic autonomy for the bloc as a process that encompasses more than simply military issues, to include, as Ms. von der Leyen said on Tuesday, matters like vaccine and semiconductor production and self-reliance.

President Emmanuel Macron of France had put initial emphasis on military capacity, both in cooperation with NATO and separate from it. That was driven by his belief that the United States was concentrating its efforts on China, not on Europe, and that the Europeans must be prepared to better defend themselves. Those views were enhanced by the strong criticism of NATO and of European defense made by President Donald J. Trump, and have only been assuaged for now by President Biden’s commitment to Ukraine and NATO.

There is considerable overlap between the European Union and NATO. Of NATO’s 30 members, 21 are also in the 27-member European Union. Should Sweden and Finland succeed as expected in joining NATO, the number will be 23 of 27, covering 96 percent of the population of the European Union, Mr. Stoltenberg said.

Another four NATO members are E.U. applicants — Albania, Montenegro, North Macedonia and Turkey — and another one, Britain, is a former E.U. member. The four non-NATO states in the bloc are the relatively small nations of Austria, Cyprus, Ireland and Malta.