US officials and politicians regularly say Washington spends 70 percent of its defense budget on North Atlantic Treaty Organisation, a claim that is flatly denied in Europe.
A senior administration official with knowledge of the situation but not authorized to speak publicly did not initially answer the question about possible troop withdrawals on a conference call with reporters.
In the interview Sunday, Flake contrasted Trump's warm words about Putin and other authoritarian figures to his harsher language for United States allies.
Many U.S. troops are there to do more than protect those countries.
On NATO's old foe Russian Federation, the administration has sent mixed messages by intensifying a USA military build-up in Europe while railing against fellow NATO members on defense spending and failing to coordinate on new sanctions on Moscow in 2017. Trump's upcoming summit with Russian President Vladimir Putin in Helsinki, Finland, has exacerbated concerns as well.
Regional experts have questioned the success of the Trump-Kim meeting, in which the president agreed to suspend US military exercises with South Korea but appeared to get little in return.
Administration officials have also said that subjects discussed with Putin would include Syria, where the administration is looking for a political settlement that would allow the withdrawal of USA troops there.
Pentagon leaders canceled military exercises there at Trump's direction but they quickly reaffirmed the United State's "ironclad commitment" to defend South Korea.
The colorful procession also featured activists wearing masks, mocking US President Donald Trump and Ukrainian leader Petro Poroshenko.
Syria war: Thousands return home in south-west
On Saturday, several rebel factions put out a statement saying they did not accept the ceasefire deal and would continue fighting. Xinhua reporters at the scene heard two explosions that rocked the vicinity, which reportedly could be the explosions of mines.
USA adds a solid 213000 jobs; unemployment up to 4 percent
Manufacturers are expected to have added another 15,000 jobs to their payrolls in June on top of the 18,000 created in May. Minutes of the Fed's June 12-13 policy meeting published on Thursday offered an upbeat assessment of the labor market.
Bill Shine joins White House as communications director
President Donald Trump on Thursday named Bill Shine , a former top official at Fox News , to be his fifth communications chief. Shine resigned in May 2017 as co-president of Fox News Channel in the wake of a sexual misconduct scandal at the cable channel.
At a reception in June celebrating 100 years of American and European partnership in Brussels, Washington's top diplomat to the European Union, Adam Shub, sought to highlight common ground, even on issues such as trade and Iran.
She said she expected unanimous agreement among NATO's 29 members on proposals to reform the alliance command structure, increase readiness for possible threats from Russian Federation on NATO's eastern flank, add a new training mission for Iraq and increase counterterrorism efforts in Afghanistan.
That may not be enough to keep Trump from raising the stakes again next week, a senior US defense official said recently. "In fact, Putin went as far as telling the President that the 'deep state" is conspiring against them both.
The protest on Saturday preceded the anti-NATO conference on Sunday, which will see dozens of activists and organizations from all over the word coming to Brussels, Iraklis Tsavdaridis, executive secretary of the World Peace Council (WPC), a self-described "anti-imperialist" global organization promoting diversity and universal disarmament, told RT.
"These are our closest allies and we really appreciate their support".
"The relationship must be reinvented every single day", he said.
The White House declined to say if and how Trump might punish the countries.
"If we are talking about the trend, then in the face of it, it can not but worry us", Zakharova said, according to state news agency RIA Novosti. "We are calling for a different kind of society".