President Trump on Friday publically confirmed his administration’s commitment to NATO's mutual defense pact known as Article 5.

Trump raised concerns among fellow NATO members last month during a speech in Brussels when he failed to mention the United States commitment to the agreement. But the president alleviated many of those fears during a news conference alongside Romanian President Romanian President Klaus Iohannis, saying that he was "committing the United States to Article 5."

“Certainly we are there to protect,” Trump said in the in the Rose Garden. “That's one of the reasons that I want people to make sure we have a very, very strong force by paying the kinds of money necessary to have that force. Yes, I would be committed to Article 5.”

A key section of the NATO treat, Article 5 commits each member state to consider an armed attack against one member state, in Europe or North America, to be an armed attack against them all. The only time Article 5 has been invoked was after the U.S. was attacked on September 11, 2001.

While the president affirmed the U.S.’s commitment to Article 5, he did not answer whether or not he would move the U.S. to defend a NATO ally if the attack came from Russia.

During the campaign and in his first months in office, Trump was highly critical of the amount that other NATO member states gave for defense spending. In Brussels last month, Trump rebuked fellow NATO members for failing to meet the military alliance's financial benchmarks, asserting that leaves it weaker and shortchanges "the people and taxpayers of the United States."

Last year, only five of the 28 countries met the two percent goal: the U.S., Greece, Britain, Estonia and Poland.

Trump’s commitment to Article 5 came as a great relief to NATO’s members from Eastern Europe, who are all greatly concerned with an increasingly aggressive Russian policy of expansionism that saw President Vladimir Putin’s forces march into the Ukraine in 2014. Romania, Lithuania, Latvia, Estonia and Poland are especially concerned about Putin’s putsch eastward given the shared land and maritime borders with their former Soviet master.

Romania’s Iohannis praised Trump's call for NATO members to increase their defense spending and touted that Romania recently boosted its own allocation of defense spending. Iohannis also stressed that necessity of NATO and the European Union to world safety.

“Your involvement makes so many nations aware of the fact that we have to share the burden in NATO,” Iohannis said to Trump during the news conference. “Romania is very conscious of the fact that we stand on the eastern flank, and we heavily rely on your partnership, President Trump, because we cannot stand there without the U.S., we cannot stand there alone.”

The Associated Press contributed to this report.