Русско-англо-русский юридический словарь

In the US, everybody says "enter into" or "sign" an agreement, not "conclude an agreement" (although they're synonymous according to the Wordref definition no. 2). "Conclusion of the agreement" is especially ambiguous because it sounds like "termination", which is the exact opposite of the intended meaning. (WordReference)

"To enter into" is more in the legally binding sense, whereas "to conclude" is more about reaching an agreement after discussion. (ProZ)