KABUL, Afghanistan – The ranking Republican on the U.S. Senate Armed Services Committee said NATO and Afghan troops will prevail in the war if they can succeed in securing and bolstering governance in the Taliban stronghold of Kandahar.

Sen. John McCain, who visited Afghanistan’s largest city in the south on Monday with two other U.S. lawmakers, warned of tough fighting ahead and predicted that casualties would rise in the short-term.

“The Taliban know that Kandahar is the key to success or failure,” McCain told a news conference at the airport in Kabul.

“So what happens in this operation will have a great effect on the outcome of this conflict. But I am convinced we can succeed and will succeed, and Kandahar is obviously the key area. And if we succeed there, we will succeed in the rest of this struggle.”

McCain, a Republican from Arizona, also reiterated his opposition to President Obama’s plan to begin withdrawing troops from Afghanistan beginning in July 2011.

Obama has said that large numbers of troops would not be pulled out if conditions did not allow, but that caveat has often gotten lost in the discussion over the length of U.S. commitment to the war.

McCain said he expected progress to be made in Afghanistan between now and July 2011. “But we must not tell the enemy that we will begin leaving when we have not finished the job,” he said.

During a two-day visit, McCain and Sen. Lindsey Graham, a Republican from South Carolina who is on the Armed Services Committee, and Sen. Joseph Lieberman, an independent from Connecticut who is chairman of the Homeland Security and Governmental Affairs Committee, met with Gen. David Petraeus, the newly installed NATO commander, Afghan President Hamid Karzai and U.S. Ambassador to Afghanistan Karl Eikenberry.