arrived at の意味は？

However, it remains unclear on what they will do in the next stage of the deal arrived at with US and Saudi mediation, according to the army.
の arrived at のところは
... in the next stage of the deal (that US and Saudi have) arrived at
と言っています。そのすぐ後ろに再度 US and Saudi が来ているので、自明かつ重複を避けるために省略されています。