Washington (CNN) -- If the United States leaves Afghanistan prematurely, the subsequent destabilization in the region would have a "huge bearing" on relations between the United States and India, Sen. John McCain warned Friday.
"Afghanistan has become a major source of tension between the United States and India, for the primary reason that India does not believe we will stay until the job is done," McCain said at the Carnegie Endowment for International Peace.
The Arizona senator, the ranking Republican on the Senate Armed Services Committee, has been a vocal critic of President Barack Obama's plan to begin drawing down troops in July 2011, saying it is a signal to the Taliban of U.S. departure.
McCain warned that if the United States leaves Afghanistan before positive conditions can be reached and maintained on the ground, the consequences will not only be troublesome for the United States, but even worse for India, "which will have a terrorist safe haven on its periphery."
Such a move would deepen India's reliance on Russia and Iran, McCain said, and would demonstrate to India that the United States is both a declining power and an unreliable partner.
The U.S. policy toward Pakistan has huge implications for the region, McCain said.
He warned that some members of Pakistan's army and intelligence service continue to support terrorist groups, largely because their belief that America will withdraw prematurely from Afghanistan pushes them to hedge their bets.
McCain credited "good luck and extraordinary restraint, especially on India's part" as the reasons that the Pakistani military's behavior has not proven catastrophic for the country.
"But if, God forbid, our luck runs out, I don't know if restraint will be an option, either for India or for us," he said.
State Department deputy spokesman Mark Toner said he agrees with McCain, but insisted no one is taking about premature withdrawal from Afghanistan.
"I don't think anybody's arguing about whether we're going to pull up stakes and head back home," Toner said.
The goal now, he said, is to build up Afghanistan's institutions and security forces. A judgment will be made next summer about how to draw down troop levels after discussions with military leaders, he said.