A stranded Russian aid convoy for Kosovo Serbs is at the center of an escalating dispute Wednesday between Moscow and international peacekeepers, with a top Western official casting doubt on the humanitarian goal of the aid mission.

The convoy of more than 20 Russian trucks was stopped Tuesday by U.S. soldiers guarding the Kosovo border with Serbia, increasing tensions in the volatile region. It remained stranded Wednesday, AP news agency reported.

Moscow has become the champion of Serb defiance against Kosovo's 2008 declaration of independence from Serbia. Local Serbs are frustrated by Belgrade's refusal to use force to save them from ethnic Albanian rule, and have turned to the Kremlin for help.

The minority Serbs, who reject Kosovo's statehood, have been blocking roads in the Serb-run north of the country to prevent Pristina authorities from taking control. The peacekeepers say the convoy's cargo consisting of canned food, blankets, tents and power generators appears like it is intended for those manning the roadblocks, and not for the general Kosovo Serb population.

"I don't know if the Russian aid is a propaganda trick or something else," the top Western official overseeing Kosovo's independence, Pieter Feith, told Serbian reporters. "Although not surprising, the (Russian aid) initiative is not practical."

"Poverty and misery exist in Kosovo, but the U.N. and the EU have not proclaimed the north of Kosovo as a zone of a humanitarian catastrophe," Feith said.

Russian officials escorting the convoy accused Kosovo's peacekeepers of blocking passage. EU officials in Kosovo said the Russians can pass if they allow an international police escort.

Russia's ambassador to Serbia, Aleksandr Konuzin, who is leading the convoy, refused an EU escort and accused the peacekeepers of "political blackmail."

Serbia's state Tanjug news agency said Konuzin asked for help from top Moscow officials.

Russia's envoy to NATO, Dmitry Rogozin, called the stoppage of the convoy "a humanitarian crime." He told Russian news channel Vesti-24 that such actions by Western countries "lead the Serbian minority in Kosovo to extinction."

The spokesman for the EU rule of law mission in Kosovo, Nicholas Hawton, said "there are two options for the convoy.

"Either they have a EULEX police escort to the destination following customs control, or proceed to Merdare," he said referring to Kosovo's eastern border crossing with Serbia that is manned by ethnic Albanian customs officials.

"It is a normal EU standard for a convoy of this size to have a police escort," Hawton said.

Konuzin has refused the alternative border crossing, saying the controls there are done by Pristina authorities, which are not recognized by Russia and Serbia.

Russia is considered a traditional Serb ally because of common Slavic roots and the Christian Orthodox religion.