The original article, for those interested.
The two sentences are similar, but have slightly different meanings.
In the article's version, we are considering all of the threats that could result from Ukraine moving toward NATO. The most immediate of all of those threats is to the peace talks, but there are other threats that are centered on entirely different diplomatic and economic (and lets hope not military) concerns.
In the version you wrote, we are considering only the threats to the peace talks, the most immediate of which is the result of Ukraine moving toward NATO. There may be other threats to the peace talks, but this is the most immediate. Any threats that do not focus on the peace talks are not considered by this sentence.
From the comments I saw something that was not immediately apparent in the version you wrote that you (Cookie Monster) did see, so good on you. The way that the second sentence reads is that the location of the threat itself is in Minsk, and it is the most immediate. I'm not sure what the threat would be that had so certain a location, but we know where it will be this week. Maybe Godzilla?
A sentence that would be more natural for your phrasing might be:
This is perhaps the most immediate threat to delicate peace talks this week in Minsk...
Where this refers to Ukraine's move toward NATO and will be is omitted entirely.