With Chancellor Angela Merkel at his side, President Donald Trump said Friday that Germany and other NATO allies have been "very unfair" to the U.S. by failing to boost military spending.

At a joint news conference with Merkel in the White House East Room, Trump first stressed "my strong support of NATO" and then renewed his campaign criticism of members of the alliance -- Germany among them -- who were not spending at least two percent of gross domestic product on defense.

"It's very unfair to the United States," Trump said. "These nations must pay what they owe -- at least two percent." The nations falling short of the goal owe "vast sums," Trump said without giving any figures.

Merkel responded that Germany had boosted defense spending by eight percent last year and was committed to reaching the two percent of GDP goal by 2024 under the agreement with all 28 members of the alliance.

Currently, five NATO nations meet or exceed the two percent goal -- the U.S. (3.6 percent), Greece (2.4), Poland (2.2), Britain (2.1) and Estonia (2.0), according to NATO statistics. The next three countries in order of contributions were France (1.8), Turkey (1.7) and Norway (1.5). Germany ranked 15th among NATO members at 1.2 percent. Luxembourg was last at 0.5 percent.

At NATO headquarters in Brussels last month, Defense Secretary Jim Mattis Defense sought to leverage the threat from Russia to prod NATO allies into spending more on common defense.

"I owe it to you all to give you clarity on the political reality in the United States and to state the fair demand from my country's people in concrete terms," Mattis told NATO defense ministers.

"America will meet its responsibilities, but if your nations do not want to see America moderate its commitment to the alliance, each of your capitals needs to show its support for our common defense," Mattis said.

In his annual report Monday, NATO Secretary General Jens Stoltenberg said that alliance members were making progress in increasing defense spending. Last year, 23 member states increased their defense expenditures in real terms by 3.8 percent, which added up to about $10 billion, he said.

He acknowledged that only five NATO members currently meet the two percent goal and added that "It is realistic that all allies should reach this goal. All allies have agreed to it at the highest level and it can be done."

Stoltenberg said that Romania plans to reach two percent his year and both Latvia and Lithuania expect to do the same in 2018.

At the news conference, Merkel appeared to shrug off Trump's history of making disparaging remarks about her. During the campaign, Trump called her tenure a "disaster" and said she was "ruining" Germany on immigration, trade and defense.

Merkel said after meeting Trump for the first time, "It's always much better to talk to one another than about one another."

Merkel also appeared to be surprised when Trump sought to use her to deflect questions about his unsubstantiated claims that the administration of former President Barack Obama tried to wiretap or surveil him.

"At least we have something in common, perhaps," Trump said in a reference to the monitoring of the cell phone of Merkel and other world leaders by the U.S. National Security Agency.

Merkel shuffled papers on her lectern as Trump made the charge, gave him a long look, and then went back to shuffling papers.

-- Richard Sisk can be reached at Richard.Sisk@Military.com.