The U.S. military campaign launched in Iraq Friday could go on for months, President Barack Obama said Saturday from the White House, but noted that he would not provide a specific timeline. 

"I'm not going to give a particular timetable," Obama said before leaving for a two-week summer vacation at Martha's Vineyard. "We are going to maintain vigilance."

Obama, who was originally against this week's military strikes and once referred to ISIL as "a jayvee team," has had to backtrack on his underestimation of the group's strength and reach. 

"There is no doubt that their advance, their movement over the last several months has been more rapid than the intelligence estimates and I think the expectations of policy makers both in and outside of Iraq," Obama said. "Part of that is not a full appreciation of the full degree to which the Iraq security forces, when they are far away from Baghdad, did not have the incentive or capacity to hold ground against an aggressive adversary."

Some critics of Obama's actions say that it appears as if the president has no plan at all for dealing with ISIL in Iraq or elsewhere. 

Sen. John McCain, who has been one of the most consistent and outspoken critics of the Obama administration's policy toward Iraq, said on Friday that what the president has done thus far has been "almost meaningless." 

"It’s almost worse than nothing because I fear the president is threatening and then he won’t follow through," McCain told The Daily Beast. "It’s the weakest possible response and we cannot allow them to take Erbil. What [the administration has] done so far is almost meaningless."

The president, however, has maintained that the long-term solution to neutralizing ISIL in Iraq is to build the unity and capacity of the Iraqi government and linking that condition to military success. 

"The most important time table that I’m focused on right now is the Iraqi government getting formed and finalized," said Obama," adding, "There has to be a rebuilding and an understanding of who it is the Iraqi security forces are reporting to, what they are fighting for."