Texas Governor and Republican White House hopeful Rick Perry on Wednesday denounced President Barack Obama for delaying the approval of a controversial US-Canada pipeline.

"This president is driven by his environmental left-leaning base that's putting pressure on him," Perry told roughly 100 people at a campaign event here two weeks before Iowa holds the first presidential nominating contest.

"He's more interested in the political position of getting elected again and making his political base happy than he is putting Americans to work," said Perry, who is running in fourth place in Iowa, according to recent polls.

Supporters say the planned Keystone XL pipeline, which would bring oil from Canada's tar sands to the United States, is the ultimate shovel-ready project that would spur the hiring of thousands of workers.

Environmental activists fear an accident along the 1,700-mile (2,700-kilometer) pipeline extension would be potentially disastrous for aquifers in central US Great Plains states.

Others oppose the multibillion-dollar project because exploiting the tar sands requires energy that generates a large volume of greenhouse gases, which scientists blame for global warming.

The Obama administration has ordered an extra environmental assessment of a possible new route through Nebraska, which could delay a final decision until after next November's election.

"Hopefully the president will understand the importance of this pipeline coming down from Canada and will approve it and it will be in construction by the time January of 2013 rolls around," said Perry, referring to the next presidential inauguration date.

But if not "that'll be one of the first things that we work on," he told the crowd at a coffee shop.

"We know that it can be done and done safely," said Perry, who predicted that the project could create "thousands of jobs" at a time of historically high US unemployment.

Obama "wants to force Americans into using green energy regardless of the cost," he charged. "No offense, Mr President, but I don't want America to look any more like Europe."