"If we are to speak about some sort of exchange, the question has not been presented in such a way, because it is not productive," he said when asked about a letter US President Barack Obama wrote to him regarding the two issues.
"Our American partners are ready to discuss this problem," added Medvedev at a joint news conference with Spanish Prime Minister Jose Luis Rodriguez Zapatero. "This is already good."
Earlier Tuesday the New York Times reported that Obama suggested in a secret letter sent to Medvedev three weeks ago that Washington would back off deployment of the missile defense shield if Moscow would help stop Iran from developing long-range missiles.
Confirming that Obama sent a letter to Medvedev, a senior US official told AFP on condition of anonymity that the missive covered "a broad range of topics including missile defense and how it relates to the Iranian threat."