This is due to the fact that the Belarusian-Russian border is open.
One of the Ukrainian representatives of the Tripartite Contact Group on Donbass Olga Aivazovskaya believes that Belarus cannot guarantee security for the negotiators, since there is no state border between the Russian Federation and the Republic of Belarus. She wrote about it on her Facebook page.
Aivazovskaya gave her subjective point of view:
"The venue for such meetings should correspond to three basic criteria, namely – the political neutrality of the host party to all the participants, logistical convenience and security guarantees, both physical and political-informational.
There is a question regarding the security, more precisely – I personally don’t feel secure enough. It does not always depend on the Minsk authorities, rather, it’s due to the absence of a Russian-Belarusian border and friendly relationships with all the consequences.
Belarus could confirm its full neutrality in the UN at the next voting on the Crimea resolution and human rights violations there," – Olga Aivazovskaya stated.