(VOVworld) - White House chief of staff Denis McDonough on Monday admitted that Obama’s administration still lacks "irrefutable evidence" on the use of chemical weapons in Syria late last month.

The US administration is facing difficulties to launch a military strike against Syria (Photo: PressTV/VOV)

Despite the admission, the White House has begun to call for support from the congress and Americans on military action against Syria. On Monday, the US congress convened the first meeting after a month of summer recess. In six separate television interviews, President Barack Obama insisted that Syrian President Bashar al-Assad should take responsibility for the sarin gas attack that killed more than 1,400 civilians. Obama noted that a military attack, once launched, would be limited and would not involve the use of ground forces. He said the US had made full use of all diplomatic channels and it’s time for Washington to take action.

On Tuesday, President Obama is scheduled to deliver a speech to politicians and then to the public, which will be broadcast live from the White House. At the same time, the White House’s top security advisors including Secretary of State, John Kerry and chief of staff Denis McDonough held both closed and open talks with lawmakers and on television.

The campaign takes place as a majority of US politicians from both the Republican and Democrat Parties remain in doubt about the efficiency of military intervention, not to mention unexpected retaliatory acts against the US and its allies once a war is launched. To date, White House officials have either met or talked with 85 out of 100 senators but it’s unknown whether or not President Obama could receive the 60 votes of support needed from the senate. In the House of Representatives, up to 190 of 435 congressmen have publicly opposed the use of armed force.