Iraq's stance in negotiations with the U.S. over the country's security has been getting tougher, a trend obviously seen when an Iraqi security officer demanded a definite deadline of U.S. troops' withdrawal.

  Iraq's President Nuri al-Maliki speaks during a visit to Kerbala, 80 km southwest of Baghdad, June 20, 2008. (Xinhua/Reuters File Photo)  

Iraq will reject any security pact with the United States unless a specific date for withdrawal of U.S.-led troops is set, Iraqi national security advisor Muwafaq al-Rubaie said in Najaf on Tuesday.

"Our stance in the negotiations with the Americans will be strong. We will not sign any memorandum of understanding without specifying a date for the withdrawal of foreign troops from Iraq," al-Rubaie told reporters in the Shi'ite holy city.

As security conditions in Iraq improve, the Iraqi government's stance in negotiations with the U.S. have become tougher. al-Rubaie's remarks were the toughest since the beginning of negotiations on a security pact between the two countries in March, analysts say.