John Kerry, the chairman of the U.S. Senate Foreign Relations Committee, says a proposal to send as many as 40,000 more American troops to Afghanistan "goes too far and too fast".
Speaking to the Council on Foreign Relations, Senator Kerry praised U.S. President Barack Obama's current review of the nation's strategy in Afghanistan.
Kerry said that after the September 11, 2001 terrorist attacks on the United States, America had to take military action.
"With certainty, we all know why we invaded Afghanistan," said John Kerry. "It was not a mistake to go in. We now have to choose a smart way forward so that no one is ever compelled to ask whether we've made a mistake in staying."
The United States has nearly 68,000 troops in Afghanistan and there are about 40,000 from NATO and other allied countries.
The top U.S. and NATO military commander there, Army General Stanley McChrystal, has warned the United States could lose the conflict if additional forces are not deployed.
The general reportedly is asking for as many as 40,000 additional troops - a figure Kerry said is too high.
"I am convinced, from my conversations with General Stanley McChrystal - and I'm grateful to him for the time he gave me there and even on the telephone since - he understands the necessity of conducting a smart counterinsurgency in a limited geographic area," he said. "But I believe his current plan reaches too far, too fast."
Kerry, during a recent trip to Afghanistan and Pakistan, is credited with playing a key role in convincing Afghan President Hamid Karzai to enter a run-off election, following wide-spread corruption that tainted the initial contest in August.
Kerry said now is not the time for a large surge of additional troops.
"We do not yet have the critical guarantees of governance and of development capacity - the other two legs of counterinsurgency," said Senator Kerry.
Kerry recommended speeding up the training and mentoring of the Afghan National Army and police so they can defend their own country.
He also said corruption must be reduced so there are honest local leaders who can partner with the United States and deliver services to restore the faith of Afghans in their own government.
The senator added that the cornerstone of U.S. strategy should be the effort to shift responsibility to the Afghan people.
"I define success as the ability to empower and transfer responsibility to Afghans as rapidly as possible, and achieve a sufficient level of stability to ensure that we can leave behind an Afghanistan that is not controlled by al-Qaida or the Taliban," he said.
Kerry warned that a quick U.S. pullout from Afghanistan could trigger a civil war. He said that a small-scale counterterrorism effort is not a viable alternative to the broader military operation now underway.