It is an accepted practice in American diplomacy to send letters to the leaders of the receiving countries together with the envoys. International scientist Suren Sargsyan wrote about this on his Facebook page. the same Samantha Power's visit to Armenia and Joe Biden's letter delivered by her to the Prime Minister. In this sense, I do not see anything unusual here. In terms of content, there is nothing unusual in the letters addressed to Aliyev and Pashinyan. It is a reflection of official American positions, with accepted wording and words of encouragement, to move forward.
The most important thing here is timing. The Biden administration has 3 months left to hand over the power to Trump or Harris. Naturally, Biden wants the 4-year contribution of his administration to the settlement of Armenian-Azerbaijani relations to reach its logical end and for Biden to justly become the godfather of the peace agreement. Outgoing President Biden, who has more experience in foreign policy than any US president in the last 30 years, understands when taking office that our region will not be a priority for either the Trump or Harris administrations, so all his achievements if even if they don't go into the water, then they will be significantly slowed down from the point of view of life. On the other hand, he wants to have in his legacy a success story in terms of peace-building, the likes of which do not yet exist. It is natural that the conclusion of a peace agreement and the resolution of the conflict in the South Caucasus (as formulated in Biden's national security strategy) are also important in the context of American foreign interests. is a circumstance, which in turn forces the Biden administration to fight for securing these interests until the last minute (January 20 at 12:00)," he wrote.
