Nuri al-Maliki said on Monday that a military agreement the two countries are negotiating should include provisions for the withdrawal of American troops.
With the country facing its lowest levels of violence in four years, Iraq's government has felt increasingly confident about its authority.
The White House said it did not believe al-Maliki was proposing a rigid timeline for US troop withdrawals.
"Negotiations and discussions are ongoing every day," Gordon Johndroe, a White House spokesman, said on Tuesday in Japan, where George Bush, the US president, was attending the Group of Eight summit.
"It is important to understand that these are not talks on a hard date for a withdrawal."