Gen. Stanley McChrystal's proposal to send 40,000 additional U.S. combat troops to Afghanistan "reaches too far, too fast," Sen. John Kerry warned Monday.

The chairman of the Senate Foreign Relations Committee said that three conditions must be met before the Obama administration decides to deploy more troops to the region: assurance that the Afghan forces are reliable enough to partner with U.S. troops, assistance from the country's local leaders, and the cooperation and support of the Afghan people.

"Under the right circumstances, if we can be confident that military efforts can be sustained and built upon, then I would support the President should he decide to send some additional troops to regain the initiative," Kerry told the Council of Foreign Relations.

Kerry said that while he believes McChrystal understands "the necessity of conducting a smart counterinsurgency in a limited geographic area," his current plan to send additional troops to the region "reaches too far, too fast."

"We have already begun implementing a counterinsurgency strategy, but I believe that right now it needs to be as narrowly focused as possible. We must be very wary of overextension," he said. 

Kerry's position would appear to rebut anti-war Democrats and others who question calls to deepen the U.S. stake in the country. At the same time, the Democratic senator would not endorse a major military increase as advocated by the commanding U.S. general in Afghanistan.

Kerry said the U.S. does not have the "critical guarantees of governance and development capacity."

"I also have serious concerns about the ability to produce effective Afghan forces to partner with, so we can ensure that when our troops make heroic sacrifices, the benefits to the Afghans are clear and sustainable," he said.

Kerry, who returned Wednesday from a seven-day trip to Afghanistan and Pakistan, also criticized the Bush administration for neglecting the eight-year-old war, saying, "You cannot understate the degree to which the Bush administration turned its back on Afghanistan completely."

Speaking of former Vice President Dick Cheney, who recently criticized President Obama's approach to redefining military strategy in Afghanistan, Kerry said that Cheney had boasted in 2002 that "the Taliban regime was out of business permanently." 

"This is one time I wish he was right," Kerry said. 

Kerry was responding to recent remarks from Cheney, in which the former vice president blasted Obama for "dithering" over the decision to send additional troops to the region.  

As Obama weighs his options on the military side, the State Department said Monday it was on track to meet the goal of tripling the size of U.S. civilian workersr in Afghanistan by year's end or very early 2010.

That will bring the number of agronomists, lawyers, diplomats and development experts in the country from 320 in January to 974, Deputy Secretary of State for Management Jack Lew told reporters.

Lew said he did not expect Obama's decision on troops to have a significant effect on the civilians except in cases where additional troops might secure new areas of the country for them to work safely.

Three civilian Drug Enforcement Administration agents died Monday during the crash of a U.S. military helicopter that also killed seven U.S. service members, an official said. The craft went down in the west of Afghanistan.

The casualties mark the first DEA deaths in Afghanistan since the drug agency began operations there in 2005.

The official spoke on condition of anonymity because no formal announcement has been made. Officials say the helicopter had left the scene of a firefight with insurgents.

The Associated Press contributed to this report.