Sen. John McCain (R-Ariz.) struck a carefully cautious tone Friday as he weighed in on President Barack Obama’s Iraq troop withdrawal plan. “The president’s plan is not without risk,” McCain, Obama’s 2008 rival for the presidency, said in a floor statement. “We have not yet completed the mission in Iraq, and the gains we have made there remain fragile.” McCain, who mightily criticized Obama’s stance on Iraq during the campaign, joined Congressional leaders at the White House Thursday for a briefing on the Iraq plan. Obama announced Friday that he will leave 50,000 residual troops in the region after a drawdown of as many as 100,000 combat troops in August 2010. Obama also plans to send additional troops to Afghanistan. “We will need to be cautious as we withdraw troops so as not to jeopardize these achievements, and listen closely to the commanders on the ground as the administration determines the pace of withdrawals,” McCain advised. On the campaign trail, McCain questioned Obama’s credentials to lead the military and criticized his pledge at the time to withdraw troops within 16 months. Obama’s plan announced Friday includes an 18-month timeline. Calling the president’s overall military plan “a reasonable one,” McCain said he was “cautiously optimistic that the plan as laid out by the president can lead to success.”