The presence of mad cow disease in Canada remained limited to one cow after test results released Sunday showed none of the other cattle on an Alberta farm at the center of the scare had the brain-wasting illness, according to a Canadian Press report.

"The rapid diagnostic test results from the originally quarantined cattle have all come back negative," said Dr. Brian Evans, chief veterinary officer for the Canadian Food Inspection Agency.

"We have seen nothing at this time through our testing results that would raise our level of concern. There is no evidence at this time to indicate the safety of Canada's beef and beef products has been compromised."

The herd was slaughtered and tested last week after a cow from the farm near Wanham, in the western Alberta Province, was found to have the first case of mad cow disease in North America for about a decade.

It is reported that an additional Alberta farm had been added to the list of those with quarantined herds. There are now 17 such farms in three Canadian provinces of Saskatchewan, Alberta and British Columbia.

Canada announced Tuesday that a cow in Alberta has tested positive for bovine spongiform encephalopathy (BSE), otherwise known as mad cow disease, the first home-grown case of the disease in North America.

So far, the United States, Japan, Australia, South Korea, New Zealand and Mexico have temporarily ban imports of Canadian beef. Canada exports beef worth about 2.7 billion US dollars a year.

US to revise tactics in Baghdad occupation

US military commanders plan to radically revise the tactics taken by their occupation force in Baghdad in the next few days to assume a more active posture, The Washington Post reported Sunday.

The US occupying troops, which have been criticized for having been too reactive and confined to fighting positions, will increase night operations and foot patrols throughout the Iraqi capital, the newspaper quoted US commanders as saying.

Also, by early next month, the US Army will fly helicopters over Baghdad for the first time. The aircraft generally will not use their weapons but instead will conduct surveillance and support ground forces with searchlights.

As part of an effort to change the image of the US force and make it seem at once more pervasive and less threatening, the big M-1 tanks that have dominated many major intersections and checkpoints for the past six weeks will be withdrawn and replaced by smaller Jeep-like Humvees, according to The New York Times.

In addition, the "footprint" of the US troop presence in the city is being expanded, with small units establishing permanent operating bases at such locations as Baghdad University, which until now has only intermittently hosted US soldiers.

The makeover is scheduled to begin in earnest at sundown Sunday, when a brigade of the 3rd Infantry Division, which charged into downtown Baghdad in early April, turns over control of the middle of the city to a fresh brigade from the 1st Armored Division.

The US military divided Baghdad into three major sectors, and US commanders describe the central sector as the most significant politically.

US ponders aggressive policy towards Iran

The Bush administration has suspended once-promising contacts with Iran and is thinking of embracing a more aggressive policy designed to destabilize the Iranian government, The Washington Post reported on Sunday.

The switch in policy came after the administration was alarmed by intelligence suggesting that al-Qaeda operatives in Iran had a role in the May 12 suicide bombings in Saudi Arabia, in which eight Americans were killed, although Tehran has rejected the US allegations.

According to the newspaper, senior US officials will meet on Tuesday at the White House to discuss the evolving strategy toward Iran, with Pentagon officials pressing hard for public and private actions that they believe could lead to the toppling of the Iranian government through a popular uprising.

The State Department, widely believed to be often at odds with the Pentagon on foreign policy issues, had encouraged some form of engagement with the Iranians in the past and now inclined to accept such a policy, especially if Tehran does not take any visible steps to deal with the suspected al-Qaeda operatives before Tuesday.

But officials from the State Department are concerned that the level of popular discontent there is much lower than Pentagon officials believe, leading to the possibility that US efforts could ultimately discredit those who Washington believes to be reformers in Iran.

In any case, the Saudi Arabia bombings have ended the tentative signs of engagement between Iran and the United States that had emerged during the wars against Afghanistan and Iraq when Tehran was perceived as relatively cooperative.