MORE EARLY SIGNS OF PROGRESS IN THE GULF…. Yesterday, around this time Adm. Thad Allen sounded very encouraged about the “top kill” efforts in the Gulf. Soon after, officials subtly walked his remarks back a bit — Allen was apparently a little over enthusiastic — and it would take more time before the results were clear.

This morning, the initial signs are, once again, generating cautious optimism.

By injecting solid objects as well as heavy drilling fluid into the stricken well leaking oil into the Gulf of Mexico overnight, engineers appeared to have stemmed the flow of oil, Adm. Thad W. Allen of the Coast Guard, the leader of the government effort, said on Friday morning. But he stressed that the next 12 to 18 hours will be “very critical” in permanently stanching what is already the worst oil spill in United States history.

Admiral Allen, who spoke on ABC’s Good Morning America, said the biggest challenge will be to sustain the “top kill” effort, which involves pumping material into the well to counteract the upward pressure of the gushing oil so that the well can be sealed.”They’ve been able to push the hydrocarbons and the oil down with the mud,” he said, referring to the heavy drilling fluid. “The real challenge is to put enough mud into the well to keep the pressure where they can put a cement plug over the top.”

BP’s chief executive, Tony Hayward, also told ABC that the efforts were “going pretty well according to plan.” He added, however, that he put the odds of success at 60 to 70 percent.

We’ll know more in 48 hours.

In the meantime, with President Obama headed to the Gulf this morning, BP has revised its estimate of the scope of the disaster. While the company initially projected a “very modest” impact, the oil company now characterizes the spill as an “environmental catastrophe.”

You don’t say.

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Follow Steve on Twitter @stevebenen. Steve Benen is a producer at MSNBC's The Rachel Maddow Show. He was the principal contributor to the Washington Monthly's Political Animal blog from August 2008 until January 2012.