Biden arrived at the gathering with a vow to reaffirm the United States' commitment to a military alliance his predecessor viewed with disdain. He placed enhanced attention on Russia and China, along with the cyber-threats emanating from both countries. A final communiqué issued by the group highlighted the "threat" presented by Russia and the "challenges" posed by China following the meeting on Monday. "I want to make it clear: NATO is critically important for US interests in and of itself. If there weren't one, we'd have to invent one," Biden said shortly after arriving during a meeting with NATO's secretary general, Jens Stoltenberg. "I just want all of Europe to know the United States is there." But Afghanistan, an issue NATO has been engaged on for 20 years after the US invoked the Article 5 common defense clause following the 9/11 terror attacks, still loomed large. Some American allies privately gripe they weren't properly consulted before Biden announced he would withdraw US troops by September 11. Some have also questioned how security can be maintained in the country when US troops leave, particularly at Kabul International Airport and other diplomatic facilities. Biden said in a news conference after the summit that there was a "strong consensus" among leaders about his plans to withdraw troops from Afghanistan. The group agreed in its final statement to provide "transitional funding" to keep the airport open, and Turkey -- a NATO member state -- committed to keeping troops in the country to safeguard the facility. The official who was present for the closed-door NATO talks said there was unanimity among countries who had contributed troops to the Afghanistan mission that the withdrawal was the right decision. "Each of them said that they ultimately agreed with the decision to draw down this year," the official said. "They understood that the time has come. And the real focus in the room was not on the question of staying or going in 2021, the real focus was on how we work together as an alliance to continue to provide support to the Afghan national security forces, the Afghan government and the Afghan people." Now, NATO leaders are discussing practical ways to maintain security in Afghanistan, including embassy presences, security training, counterterrorism efforts and economic aid. The official said despite reports of friction among NATO allies over the Afghanistan decision, "that is not the vibe in the room today." "There's an incredible amount of warmth and unity around the entire agenda, including the 'in-together-out-together' aspect of the Afghanistan drawdown," the official said.