The Pentagon on Friday condemned Russian forces for sending a 90-truck convoy into Ukraine and demanded that they remove their vehicles and personnel from the territory “immediately.”

Russia has argued that the trucks are loaded with humanitarian aid for pro-Russian separatists fighting the Ukrainian army.

But Ukraine and its allies have resisted allowing them to cross the border, believing they could be a Trojan horse and arguing that Russia should allow the International Red Cross to inspect and deliver the supplies.

After trying to negotiate their entry over the last day, Russians lost their patience and sent the convoy in Friday morning.

The Pentagon’s spokesman, Rear Adm. John Kirby, said the actions amounted to yet another escalation of tensions in the region, as well as a violation of Ukraine’s sovereignty.

Adding to the tensions and concerns about an invasion, there are upwards of 10,000 Russian troops amassed at the Ukrainian border.

“Russia should not send vehicles, persons or cargo of any kind into Ukraine, whether under the guise of humanitarian aid and convoys or any other pretext without Kiev’s express permission,” Kirby said. “Russia must remove its vehicles and its personnel from the territory of Ukraine immediately. Failure to do so will result in additional costs and isolation."