Environmental groups have for months been pushing Obama to make good on a threat he issued to lawmakers in February in his State of the Union address: "If Congress won't act soon to protect future generations, I will." Obama's move to take the matter into his own hands appears to reflect a growing consensus that opposition in Congress is too powerful for any meaningful, sweeping climate legislation to pass anytime soon. "They shouldn't wait for Congress to act, because they'll be out of office by the time that Congress gets its act together," Rep. Henry Waxman, the top Democrat on the House Energy and Commerce Committee, said in an interview. Another key issue hanging over the announcement - but unlikely to be mentioned on Tuesday - is Keystone XL, a pipeline that would carry oil extracted from tar sands in western Canada to refineries along the Texas Gulf Coast. A concerted campaign by environmental activists to persuade Obama to nix the pipeline appears to be an uphill battle. The White House insists the State Department is making the decision independently. Obama's speech on Tuesday will come the day before he leaves for a weeklong trip to three African nations.