U.S. intelligence has established timeline of Syrian chemical attack, officials say The Obama administration believes that U.S. intelligence has established how Syrian government forces stored, assembled and launched the chemical weapons allegedly used in last week's attack outside Damascus, according to U.S. officials. The administration is planning to release evidence, possibly as soon as Thursday, that it will say proves that Syrian President Bashar al-Assad bears responsibility for what U.S. officials have called an "undeniable" chemical attack that killed hundreds on the outskirts of the Syrian capital. Paul Danahar, author of "The New Middle East" and former BBC Middle East bureau chief, explains how the Obama administration's red line leaves it with no other option than to take action in Syria. The report, being compiled by the Office of the Director of National Intelligence, is one of the final steps that the administration is taking before President Obama makes a decision on a U.S. military strike against Syria, which now appears all but inevitable, "We are prepared," Defense Secretary Chuck Hagel told the BBC on Tuesday. We have moved assets in place to be able to fulfill and comply with whatever option the president wishes to take. We are ready to go. The assets include four cruise-missile-armed destroyers in the Mediterranean. The timing of such a military response is being dictated by the need not only to assemble incontrovertible evidence against Assad - an important prerequisite for the administration, and the country, given the recent memories of a war based on false claims of weapons of mass destruction - but also to allow consultation with Congress and international partners. Britain, France and Turkey have indicated willingness to contribute to military action. The administration is weighing the importance of direct international participation in an effort that U.S. forces are prepared to undertake themselves. The safety of United Nations experts who are in Syria investigating the chemical weapons allegations is also an issue, said a senior administration official who spoke about internal deliberations on the condition of anonymity. The U.N. experts, who on Monday conducted the first of what was to be four days of on-site inspections, postponed their Tuesday visit because of security concerns. Reports of the Aug. 21 attack in the Ghouta area outside Damascus derailed their original plans to visit three other sites in western Syria where chemical strikes allegedly occurred earlier, and the permission granted by the government for a two-week stay expires Sunday. "We are concerned about the possibility that the Syrian government would seek to delay access and negotiate so as to seek to keep this [inspection] process going and avert the consequences," the administration official said. Ongoing government shelling of Ghouta and surrounding areas, the official said, "is creating more time and space for them to seek to cover things up and delay." One question that is unlikely to be addressed in the intelligence report is why Assad would launch such a massive chemical strike in the face of a near-certain international response. It is a question that Russia, Assad's principal international backer, has raised repeatedly in suggesting that Syrian rebels arranged the attack to implicate the government.