Mr Lavrov (R) said Russia should have a "permanent presence" at the sites
Russia has demanded permanent access to planned US missile defence sites in eastern Europe, if agreement is to be reached on the proposed missile shield.
Russian Foreign Minister Sergei Lavrov said this was a sticking point in Moscow's negotiations with Washington.
A new arms race could be sparked if the US failed to address Russian concerns on the issue, he said.
Russia has strongly opposed the defence system, which the US says is necessary to block attacks by states like Iran.
The US wants to locate a radar base in the Czech Republic and an interceptor missile site in Poland.
"In all these many proposals we are interested only in two things - the permanent presence of our officers and reliable technological means of monitoring [activity at the sites]," Mr Lavrov told Russian radio.
"For us it is important that we should see second-by-second where that radar is looking, and what is happening at the... base in the Czech Republic."
The US has proposed that Russian officers be granted frequent access to the sites, but not be based at them permanently, he said.
Both Poland and the Czech Republic "don't even want to hear about a permanent Russian presence", he added.
At their last scheduled summit in Russia during the weekend, outgoing Russian President Vladimir Putin and US President George W Bush promised to work for an agreement on the missile defence programme, but failed to clinch a deal on the plan.