Hollywood veteran Robert Redford has called on President Barack Obama to "stand up" and honor his pre-election pledge to get tough on environmental issues.

The Sting star is a vocal campaigner for green issues and was a prominent supporter of Obama during his 2008 election campaign.

But he's now written a stinging column for the Huffington Post in which he outlines his doubts over the U.S. leader's commitment to environmental protection.

He writes, "One reason I supported President Obama is because he said we must protect clean air, water and lands. But what good is it to say the right thing unless you act on it? Since early August, three administration decisions - on Arctic drilling, the Keystone XL pipeline and the ozone that causes smog - have all favored dirty industry over public health and a clean environment. Like so many others, I'm beginning to wonder just where the man stands."

After detailing his areas of concern, Redford adds, "What's going on here? In all three cases, the administration's decisions have come in the face of a withering industry lobbying campaign based on the usual mix of fear mongering and lies... I want our smog levels to come down so more of our children and seniors can breathe clean air. Putting corporate profits above public health is unconscionable. It's outrageous that it would be countenanced - by this president or any other.

"President Obama has done a lot to protect public health and our environment... But we have to keep moving forward. This is no time to turn back from the progress we need. I have to believe that President Obama still knows it's important to protect clean air, water and lands. Like so many, I'm waiting for him to stand up for all that."

"I'm waiting for him to stand up for our future. But we can't wait forever."