BRUSSELS -- U.S. President Trump has reportedly renewed his sharp criticism of NATO allies at the alliance's Brussels summit on July 12 -- leading to a previously unscheduled, allies-only meeting.

The emergency meeting took place after a session on Black Sea security and before a scheduled session on Afghanistan.

German Chancellor Angela Merkel said after the closed-door talks that there was 'clear commitment to NATO' by all in alliance's emergency session.

Meanwhile, Washington announced that Trump would hold a press conference in the aftermath of the unscheduled talks.

Reuters quotes two unnamed sources who said Trump launched a fresh attack against NATO allies about their defense spending and European trade practices during a session that was meant to focus on Black Sea security.

They said that, following Trump's criticism, which singled out Germany and Spain, NATO leaders asked the presidents of non-member NATO partner states Ukraine and Georgia to leave the room so they could conduct the emergency 'allies-only' talks.

AFP quoted an unnamed diplomatic source as saying that during the closed-door session with Ukrainian President Petro Poroshenko and Georgian President Giorgi Margvelashvili, 'Trump took advantage of his speaking time to return to the issue of burden sharing' -- prompting NATO Secretary General to convene the emergency meeting,

Earlier on July 12, Trump had tweeted during a summit session that NATO countries 'Must pay 2% of GDP IMMEDIATELY, not by 2025.'

Trump on July 12 also tweeted: "The U.S. pays tens of Billions of Dollars too much to subsidize Europe, and loses Big on Trade!"

Trump has previously called on other NATO states to meet a commitment made in 2014 to spend 2 percent of their gross domestic product on defense by the end of 2024.

He stunned his European counterparts on July 11 by calling on them to double their commitments on military spending to 4 percent of GDP.

According to NATO statistics, that's a bigger share than the United States currently pays.

Trump's latest outburst may come as a blow to NATO leaders who had been hoping for a less confrontational tone on the final day of their summit in Brussels, a day after U.S. President Donald Trump accused Germany of being 'captive' to Russia for energy and demanded that alliance members double their commitments on defense spending.

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Key sessions on July 12 had been planned to focus on the war in Afghanistan, as well as security in the Black Sea region following increasingly aggressive actions by Russia -- including the war in eastern Ukraine between the Kyiv government's forces and Russia-backed separatists.

'Regional Challenges'

Earlier, NATO Secretary-General Jens Stoltenberg had said the talks would 'address regional challenges' in the Black Sea as well as 'defense reforms and NATO's continuing support.'

Georgian Foreign Secretary Tengiz Pkhaladze noted last week that it was 'the first time in the history of NATO-Georgia relations' that a meeting was being held 'at the highest level with the participation of the heads of state.'

The emergency talks on July 12 set back what was meant to be the final session of the summit -- a gathering of leaders from countries involved in the NATO-led Resolute Support mission in Afghanistan.

Afghan President Ashraf Ghani was invited to that session along with the leaders of NATO partner states that are not members of the alliance but are contributing forces to Resolute Support.

Stoltenberg said on July 11 that he expects NATO leaders to 'agree to extend funding for the Afghan forces beyond 2020,' and to express full support for Ghani's 'bold peace initiative' and government reforms.

Despite apparent tensions between the transatlantic allies, the first day of the NATO summit produced a strong statement criticizing Russia and calling for 'fair burden-sharing.'

'We will continue to stand together and act together, on the basis of solidarity, shared purpose, and fair burden-sharing,' the statement said.

'Clear Signal' To Russia

NATO also reaffirmed its rejection of Russia's forcible annexation of Ukraine's Crimean Peninsula in 2014.

Stoltenberg said Russia's move was 'one of the main reasons why NATO has implemented the biggest reinforcement of collective defense since the Cold War' and has increased its presence in Poland, the Baltics, and Black Sea states that are NATO partners.

NATO is sending Russia 'a very clear signal that anything similar to what happened in Crimea cannot happen against any NATO country,' Stoltenberg said.

The NATO statement also extended an invitation to Macedonia to join after it implements its settlement of a long-running name dispute with NATO member Greece.

NATO leaders in Brussels have indicated concerns about a meeting in Helsinki planned for July 16 between Trump and Russian President Vladimir Putin.

Trump shocked some by saying on July 10 that the NATO summit might be more difficult than his talks with Putin.

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But British Prime Minister Theresa May has welcomed the Trump-Putin talks, saying they should be used to lower the risk of conflict between NATO and Russia.

According to May's spokesman, the British leader offered an upbeat assessment of the Trump-Putin meetings during a dinner for NATO leaders late on July 11.

'Open channels of communication between the U.S. and Russia are key to managing the risks of confrontation,' May was quoted as saying.

May also highlighted what she called Moscow's 'malign activity,' including Kremlin-linked cyberattacks on the West and the use of a Soviet-era nerve agent against a former Russian spy on British soil, the spokesman said.

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