Originally Published: 30 JUN 22 10:45 ET

By Natasha Bertrand, CNN

(CNN) -- NATO military officials said Secretary-General Jens Stoltenberg's announcement earlier this week that 300,000 troops would be placed on high alert across the alliance is something the alliance will work on going forward, rather than an immediate shift.

Stoltenberg said on Monday that NATO "will transform the NATO Response Force and increase the number of our high readiness forces to well over 300,000." But it now appears that number is more aspirational, and is based on a new model NATO believes will take at least another year to accomplish.

The initial announcement appeared to be a seven-fold increase from the 40,000 troops NATO currently has on high alert. Two NATO officials told CNN that number caught many NATO countries' defense chiefs off guard.

It was not clear to them, for example, which troops from each member state would need to contribute to that new high-readiness force, or whether enough countries had even been asked or agreed to provide the sufficient forces for it. It was a point of apparent confusion and disjointedness in an otherwise highly choreographed show of unity among the allies.

Two senior NATO officials told reporters in a briefing on Thursday that the new high-readiness model will eventually replace the NATO Response Force model, but that it is "still a work in progress."

"We know from nations, through our planning process, the number of forces that nations have at their disposal, the readiness that they have," one of the officials said. "So, there will be several iterations of populating this model, but we would not be giving figures for a model if we were not extremely confident that we could deliver on those things. But it's a work in progress."

The high-profile summit saw NATO formalize its invitation to Sweden and Finland to join its alliance Wednesday, a historic expansion of the defense bloc. The group collectively decided to approve countries' applications to join after Turkey dropped its objections Tuesday, paving the way for NATO's most consequential enlargement in decades. The decision will now go to the 30 member states' parliaments and legislatures for final ratification. NATO's leaders said they expected the process to move quickly, allowing for an unprecedentedly swift accession and a show of unity against Putin.

The expansion vote, paired with substantial new commitments bolstering NATO's force posture in Europe, combined to make this week's summit in Madrid one of the most productive in recent memory. The alliance endorsed a new "Strategic Concept" document that outlines the NATO's goals for the next decade. The document, last updated in 2010, lays out the security challenges facing the defensive alliance while outlining a course of actions.

For the first time, the document outlined the China "challenge," saying that the country's "ambitions and coercive policies challenge our interests, security and values." This was the first time the Strategic Concept document mentioned China; the 2010 version made no mention of Beijing. It also states that climate change is "a defining challenge of our time."

The document identifies Russia as the "most significant and direct threat to allies' security and to peace and stability in the Euro-Atlantic area" and addresses NATO's support for an independent Ukraine. In the 2010 version of the document, Russia was referred to as a "Euro-Atlantic partner."

The officials indicated that under the new model, many of the troops would remain in their home countries rather than move under the command of NATO's Allied Command Operations. But they would be quickly available to NATO should a security crisis arise, such as if Russia were to attack a member country.

Asked what the trigger would be to move those forces to high alert under NATO command, one of the officials would only say it will involve "indications and warnings" of a potential attack.