NATO chief Anders Fogh Rasmussen urged calm in Kosovo Thursday as tensions rose in its northern region after warnings Pristina could take control of disputed border crossings with Serbia.
"I look to all communities and all leaders to show the utmost care in their actions in the coming days so they create a more secure future not a more unstable (one)," Rasmussen said, warning that unilateral moves by any side would be "unhelpful".
"There can be no turning back. NATO has spent 12 years ensuring stability and security. We will not allow that achievement to be put at risk," he said, in his first visit to the region since the NATO-led KFOR troops stepped in to quell violent clashes following a trade row late July.
Kosovan Prime Minister Hashim Thaci stressed again that his government would take control of the disputed border posts on Friday.
"The operational plan (to re-establish control) enters into force on 16 September," he said.
NATO'S 6,000-strong KFOR force is currently manning the posts, but Pristina wants to put ethnic Albanian customs officials in their place, a move rejected by Serbia.
Belgrade has accused Pristina of taking unilateral action to change the reality on the ground.
"The unilateral action ... concerning an attempt by Pristina and the (EU-mission) EULEX to impose customs control at (the crossings) in Northern Kosovo would seriously endanger the peace and stability of the whole region," Serbian President Boris Tadic warned Thursday.
"Such a solution was not agreed by Belgrade and Pristina" at EU-mediated talks in Brussels, he stressed.
Tensions were high Thursday in Kosovo's only truly divided city Kosovska Mitrovica where Serbs a day earlier blocked the main bridge over the Ibar river, a flashpoint of ethnic tensions that divides ethnic Serbs in the north of the town from ethnic Albanians in the south.
By blocking one of the main arteries between Serb-dominated northern Kosovo and the rest of the territory they hope to stop Pristina from sending police in to take over the crossings.
In July, the Kosovo government dispatched special police to take over the two posts to enforce a ban on imports from Serbia that was imposed in retaliation for an earlier Serbian ban on goods from Kosovo.
The ban came in protest at Kosovo's 2008 declaration of independence.
Kosovo said it needed to install ethnic Albanians at the two posts, because Serb guards were not enforcing the ban.
Serbs in northern Kosovo then clashed with the police, killing one ethnic Albanian police officer. Four others were injured in the ensuing violence.
To stop the situation from deteriorating further KFOR -- which has overseen security in the ethnic Albanian-majority territory since the war with Serbia ended in 1999 -- took control of the crossings.
After both sides reached a deal during Brussels-mediated talks to solve the trade row, the embargos are expected to be lifted Friday, but instead of easing tensions, Pristina's announcement that it would send its own customs officials has caused further concern.
Kosovo's declaration of independence from Serbia in 2008 has been recognised by more than 80 countries including the United States and most of the European Union.
Serbia, which considers the region the cradle of Serb civilisation, rejects independence.