Russia President Vladimir Putin has declared a moratorium on the 1990 Conventional Forces in Europe Treaty after saying the Nato signatories of the pact had not ratified it and did not respect its clauses.
He said the decision was linked in part to a US plan to station elements of a missile shield in Poland and the Czech Republic; Moscow has said the plan threatens its national security.
The treaty was signed by the United States and 21 other Nato and World Trade Organization (WTO) countries in Paris in 1990. It created a military balance between two "groups of states-parties" - corresponding at the time to Nato and the WTO - by reducing to equal levels the holdings of each group in five categories of conventional weapons.
"[Nato countries] are . . . building up military bases on our borders and, more than that, they are also planning to station elements of anti-missile defence systems in Poland and the Czech Republic," Mr Putin said.
"In this connection, I consider it expedient to declare a moratorium on Russia's implementation of this treaty - in any case, until all countries of the world have ratified and started to strictly implement it," Mr Putin said in his annual address to both houses of parliament.
In the speech Mr Putin also said that foreign money was being used to meddle in Russia's internal affairs and called for tougher laws to fight "extremism".
"Some people are not averse to using the dirtiest methods, trying to foment inter-ethnic and religious hatred in our multinational country. In this respect, I am addressing you with a request to speed up the adoption of amendments to the legislation toughening punishment for extremist actions," he told an audience that included members of Russia's parliament.
In a clear reference to the opposition, Mr Putin said there were internal forces in Russia that dislike its political stability and steady economic growth and wanted to steal its natural resources.
He said they were playing into the hands of foreign "colonialists" willing to control Russia.
Mr Putin is due to step down next year when his second and last four-year term ends. He is widely popular while the economy is fast-growing, propelled by revenues from booming oil exports.
The United Russia party which he patronises is expected to perform well in a parliamentary election due in December.
Police have recently violently dispersed several opposition rallies, drawing strong criticism from the West and human rights bodies.