NAJAF (AFP) - Iraq said on Tuesday it will not reach any security pact with Washington unless it sets a date for the pullout of US-led foreign troops, a proposal turned down by US President George W. Bush. The Shia-led government's demand - which was swiftly rejected by Washington - underlines Iraq's new tougher stand in complex negotiations aimed at striking a security deal more than five years after the US-led invasion. "We will not accept any memorandum of understanding if it does not give a specific date for a complete withdrawal of foreign troops," national security advisor Muwaffaq al-Rubaie told reporters in the holy city of Najaf. Baghdad and Washington are negotiating a deal that would see the presence of US-led forces beyond 2008 when the UN mandate which provides the legal basis for a foreign troop presence in Iraq expires. The security pact, also known as Status of Forces Agreement (SOFA), has to be signed by July 31 according to a previous agreement between Bush and Iraqi Prime Minister Nuri al-Maliki, but it has provoked strong opposition in Iraq. And the US State Department rejected the Iraqi demand for a specific timetable. "The US government and the government of Iraq are in agreement that we, the US government, we want to withdraw, we will withdraw. However, that decision will be conditions-based," State Department spokesman Gonzalo Gallegos said. Rubaie said it was proving "very difficult" to set a date. "The Iraqi government has spoken about its date, while the foreign party has spoken about its date," he said. "Until now we have not arrived at an agreement on this issue." On Monday, the White House reacted to Maliki's comments by saying it was not negotiating a "hard date" for a US withdrawal from Iraq but it did not rule out discussions on "time-frames" with Baghdad. White House spokesman Scott Stanzel said the talks were aimed at reaching agreement on a framework for future US-Iraqi relations and on the arrangements to govern the US military presence. "It is important to understand that these are not talks on a hard date for a withdrawal," he said. "When you make an agreement," he added, however, "that doesn't mean that there won't be some understanding of time-frames."