The NATO secretary-general recalled that each member has submitted a plan outlining how it will achieve the commitment made in 2014, when at a summit in Wales the allies agreed that, within a decade - to 2024 - they would ensure defence spending reached two percent of GDP.
The secretary general expressed the view while addressing a press conference on Thursday after the North Atlantic Treaty Organisation defence ministers meeting in Brussels, the capital of Belgium.
Afrin - a region bordering Turkey's southern Hatay and Kilis provinces - has been controlled by the PYD/PKK terrorist group since 2012, when Syrian regime forces withdrew from the area.
Speaking at the meeting Thursday, Mattis reflected on the situation on the ground between different groups fighting the Islamic State. "Not tonight, we're still working", he said.
Tillerson, who is on a five-city tour, told a news conference in Beirut before arriving in Ankara that the United States and Turkey had the same main objectives, and put their differences down to tactics.
"Turkey has been a key member of that coalition", he said. However, Tillerson later said that Washington had "never given heavy arms" to the YPG and there was therefore "nothing to take back".
The Turkish minister also reported Mattis as saying the US was developing plans to take back weapons supplied to the Syrian Kurds. We have seen the reports, but it's not for me, in a way, to have any€¦ to give advice on that, it's for the Afghan government to decide.€.
"Turkey has some legitimate security concerns".
The United States, the MP added, will continue doing everything possible to force Russian Federation to inform Washington about all military components of Russia's defence, especially when it comes to Iskander missile systems, because "this is a state-of-the-art weapon that poses a serious threat to Western countries".
Tillerson said the first committee would begin working in mid-March and deal with the issue of the town of Manbij, held by the USA -backed Syrian Kurdish militia and where the United States has a military presence. Turkey's military campaign against Kurds in northern Syria has alarmed the US leaders who have watched as the fighting has sapped energy from the fight against remaining IS strongholds.