US Democrat's health is improving

Democrat Tim Johnson, 60, of South Dakota, who suffered from bleeding on the brain, had been in a "critical" condition following the operation.

The Democrats control the upper house of the US Congress by a single seat.

If Mr Johnson stands down, the Republican governor of South Dakota will name his successor.

That person - likely to be a Republican - would serve until the next general election in 2008.

'Next step'

Mr Johnson's spokeswoman, Julianne Fisher, told news agencies that the senator's condition "had been upgraded from critical to fair".

"The senator continues to make progress," she said, adding: "The next step would be rehabilitation and we hope that would happen within the week."

Mr Johnson was admitted to George Washington University hospital on 13 December after experiencing what his office initially said was a possible stroke.

According to the hospital, a health status of "fair" means that vital signs like blood pressure and temperature are stable and within normal limits.

Mr Johnson had prostate cancer in 2004 but says he is now clear of the disease. His wife has also suffered from cancer.

There is little precedent for forcing a living senator to stand down against his will.

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Senator Tim Johnson
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