In an interview with the Ekho Moskvy radio station on Tuesday, Lavrov said: "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].
"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.
"In the proposals which we have received (from US negotiators)... there is no mention of a permanent presence, it says that officers can be posted to the Russian embassies in Poland and the Czech Republic and work at these sites on the basis of reciprocity."
He said that without permanent access to the sites "this whole scheme of providing these measures for improving confidence is rendered worthless."
Asked to respond to Lavrov's comments, Tomas Pojar, the Czech Republic's deputy foreign minister, said: "A permanent presence is not something we would be considering.
"If Russians really care about transparency, it could be secured by a combination of several methods ... We offered liaison officers with access to the base."
Washington says the missile shield is needed for protection from missile strikes by what it calls "rogue states," specifically Iran.
Moscow says it believes the radar will be used to monitor its territory and has called the US plan a threat to the fragile balance of forces in Europe.
An informal summit on Sunday between Vladimir Putin, Russia's president, and George Bush, the US president, failed to bridge the main differences on the missile defence system.
But Putin said after the meeting that he felt Washington had heard Moscow's concerns and expressed hope that adequate confidence-building measures would help allay them.