The United States says the Islamic State militant group has at least two times as many fighters as an earlier estimate. The U.S. Central Intelligence Agency says the group now has between 20,000 and 31,500 fighters in Iraq and Syria. The old estimate was 10,000. A CIA official reported this week that the new number is based on more people joining the militants since June. He noted the success of militant forces in battle and their declaration of an Islamic state.The new intelligence estimate came a day after President Barack Obama announced his plan for defeating the group. Mr. Obama said he is expanding the U.S operations against the militants to include air strikes in Syria. He said his administration will build an international coalition to defeat Islamic State forces. He also said that no U.S. troops will return to battle in Iraq.The president made the announcement Wednesday night in a speech to the American people. Some observers say his plan represents the beginning of a long campaign involving U.S. forces. Mr. Obama recently came under criticism for saying he did not have a strategy for the militants.For weeks, the U.S. aircraft have been attacking Iraqi territory controlled by Islamic State forces, also known as ISIL. President Obama announced on Wednesday that the air strikes will be expanded to militant positions in Syria."We will hunt down terrorists who threaten our country, wherever they are. That means I will not hesitate to take action against ISIL in Syria, as well as Iraq. This is a core principle of my presidency. If you threaten America, you will find no safe haven."The president did not say when the air strikes will end. Some U.S. officials say they could last for years.Mr. Obama also announced plans to send 475 armed forces members to Iraq. They will join the more than 1,000 already serving as advisors in the country.The president said the U.S. aim is to break down and later destroy the militant group. Islamic State fighters recently executed two American journalists. Americans have been shocked by images of the killings.Opinion surveys this week showed a majority of Americans support action against the militants. After the speech, the two main parties expressed support for military strikes against Islamic State forces. Mitch McConnell is the top Republican in the U.S. Senate."I'm glad the president has brought a new focus to the effort against ISIL. He needs to take this responsibility head-on. This congress, the next congress, and the next administration have serious work ahead as we consider this multi-year commitment and what it will take to defeat ISIL."Yet Republicans and Democrats disagree about what will be required to defeat the militants. House Speaker John Boehner says air strikes involving U.S. fighter aircraft will not be enough."An F-16 is not a strategy, and air strikes alone will not accomplish what we are trying to accomplish. And the president's made clear he doesn't want U.S. boots on the ground. Well, somebody's boots have to be on the ground."Senator Barbara Boxer of California belongs to the Democratic Party. She supports Mr. Obama's call for an international coalition to defeat the Islamic State."Beware of the people here who were the cheerleaders of the Iraq War, who want to get this president to now say is gonna put combat boots on the ground. That is the wrong recipe. We learned it -- 4,000 dead Americans."President Obama is seeking congressional approval to train and supply Syrian opposition fighters. He wants them to battle Islamic State forces operating in Syria. That training would take place in Saudi Arabia, which U.S. officials say has promised to assist the efforts.And that's In The News from VOA Learning English.