The U.S. presidential race between Barack Obama and Mitt Romney is very close in four of the critical battleground states expected to decide next week's election, but Obama has built a small lead in Virginia, according to a Reuters/Ipsos poll released on Thursday.

The incumbent Democratic president leads his Republican challenger by five percentage points among likely voters in Virginia, at 49 percent to 44 percent.

That margin exceeds the survey's 4-point credibility interval, the tool used to account for statistical variation in Internet polls.

Obama has two-point leads among likely voters in both Ohio and Florida, leaving those races statistically tied.

Romney leads by one point in Colorado, edging Obama by 47-46 percent, effectively another dead heat.

With the national race tied or nearly so in most polls, the presidency will be decided in a handful of hotly contested swing states where the battle for the White House is now mostly considered too close to call.

The trends are important despite the small size of the leads, Ipsos pollster Julia Clark said, especially in Virginia, where Obama led by just two points in poll results released on Wednesday.

"It will be one to watch very closely in the next few days," she said.

Clark said the result was not affected by superstorm Sandy, which hit parts of Virginia early this week but did not cause devastation anywhere near the impact in hard-hit New Jersey and New York. Reuters