Iraq's government spokesman has said the United States' offers of changes to a draft security agreement are "not enough" and asked Washington to offer new amendments if it wants the pact to win parliamentary approval.
The comments on Monday by Ali al-Dabbagh were the first by the Iraqis since the US submitted a response last week to an Iraqi request for changes in the draft agreement.
The agreement would keep US troops In Iraq until 2012 and give Iraq a greater role in the management of the US mission.
Al-Dabbagh said his remarks constituted the government response but it had not been officially conveyed to the Americans.
However, on Tuesday Al-Dabbagh told Al Jazeera that there was optimism from Baghdad that a deal with the US would be made.
There was no immediate comment from US officials, who had described the latest draft submitted to the Iraqis as a "final text".
Privately, however, some US officials have said they expect protracted haggling over the agreement, with the Iraqis pressing for more concessions until the last minute.
"There are still some points in which we have not reached a bilateral understanding," al-Dabbagh told the Associated Press news agency.
He said the government was inviting the US "to give answers that are suitable to the Iraqis".
The agreement must be approved by parliament before the Decemeber 31 expiration of the UN mandate that allows US troops to operate legally.
Without an agreement or a new UN mandate, US military operations would have to stop as of January 1, 2009.
Al-Dabbagh did not spell out in detail what points the Iraqis still find unacceptable, but they probably include Baghdad's demand for expanded legal jurisdiction over US soldiers.
The current draft allows Iraqi courts to prosecute soldiers accused of major, premeditated crimes allegedly committed off post and off duty.
The Iraqis had asked for elaboration on those charges and a greater role in determining whether specific cases met the criteria for trial in their courts.
But the agreement faces strong opposition, especially within the majority Shia community which is the base of political support of Nuri al-Maliki, the Iraqi prime minister.