Prime Minister Nuri al-Maliki told the Syrian foreign minister on Monday that he was not prepared to let Iraq become a proxy battleground for Syria's differences with the United States.
"If Syria or any other state has differences with the United States, it's their own business," Maliki said.
"It should settle these differences, but not at our cost," the premier told a joint news conference with Foreign Minister Walid Muallem, the first Syrian official to visit Iraq since the US-led invasion of 2003.
Maliki said Iraq aimed to improve relations with Syria, but "this requires a strong desire from both the brother countries".
Syria should be "more understanding towards us," he said, adding: "What goes on in Iraq is a threat for everybody. The interest of Syria is to contribute in the stability of Iraq."
Muallem denied Syria wanted to see instability grip its eastern neighbour.
"Danger to Iraq is danger for the entire region," he said,
"We want to increase co-ordination in security and political fields with Iraq. We want to be a partner in the benefits and in the losses."
US authorities have regularly accused Syria of not doing enough to prevent Sunni Arab insurgents smuggling men and materiel across its border with Iraq.
Coalition spokesman Major General William Caldwell said on Monday that up to 70 foreign fighters a month were slipping across the border from Syria.
But Muallem denied that his landmark visit was an attempt to "appease the United States".
"I am not a mediator of the United States in the region and there is no dialogue between Syria and the United States," he told an earlier news conference.
"I did not come to Iraq to appease the United States or any other party."
British Prime Minister Tony Blair has urged US President George W. Bush to involve Syria and its regional ally Iran in efforts to stabilise Iraq.