The continuation of the 14th meeting, which was held on 21 May, was to have taken place in Belgrade today.
The cancellation prompted the above-mentioned four countries to send the letter to Serbia's ministry expressing their surprise and regret.
The four countries also hold that Serbia had enough time since the signing of the Zagreb resolution in December 2006 to prepare the takeover of facilities and to relocate its diplomatic staff from buildings allocated to other countries-successors.
The deadline for the transfer of a total of 44 facilities covered by the resolution is the end of June 2011.