The televised address to his nation by President Aleksandar Vucic followed the collapse of political talks between Serbian and Kosovo leaders earlier this week mediated by the European Union in Brussels.
Serbia, along with its allies Russia and China, has refused to recognise Kosovo's 2008 declaration of independence.
A Nato-led intervention in 1999 ended the war between Serbian forces and separatists in Kosovo, and stopped Belgrade's bloody crackdown against Kosovo's majority Albanians.
The EU has overseen years of unsuccessful talks to normalise their ties, saying it is one of the main preconditions for Kosovo and Serbia's eventual membership in the 27-nation bloc.
"We have nowhere to go, we are cornered," Mr Vucic said. "We will save our people from persecution and pogroms, if NATO does not want to do it."
He also claimed that Kosovo Albanian "gangs" need to be stopped from crossing into northern Kosovo, where most of the Kosovo Serbs live. He offered no proof for the claim.
There are widespread fears in the West that Russia could encourage its ally Serbia into an armed intervention in northern Kosovo that would further destabilise the Balkans and shift at least some world and NATO attention from Russia's war in Ukraine.
Nearly 4000 NATO-led peacekeepers have been stationed in Kosovo following the 1998-99 war and any armed intervention there by Serbia or Russia would mean a major escalation of a simmering conflict in Europe.
Following the collapse of the EU-mediated talks, NATO peacekeeping troops in Kosovo have been deployed at main roads in its north, saying they are ready to protect the freedom of movement for all sides.
Tensions between Serbia and Kosovo soared anew last month when the Kosovo government led by Prime Minister Albin Kurti declared that Serbian identity documents and vehicle licence plates would no longer be valid in Kosovo's territory.
Serbia has been implementing the same measures for Kosovo citizens crossing into Serbia for the past 10 years.
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