Gates, whose public statements suggest he also supports additional troops, says that discussions on the issue with NATO allies have moved forward even before the Afghan presidential runoff has occurred.
"I think my view all along has been we ought to do this in a way that if Gen. McChrystal has an additional set of needs, it should not be looked upon as exclusively the responsibility of the United States to respond," Gates said Tuesday night during a press conference in Tokyo, Japan.
Karzai's decision to support a runoff election – brokered chiefly by Sen. Kerry, after days of negotiations – could buy Obama some more time and play to his advantage.
"This is not an excuse for indefinite delay, but the significance of this decision that he's making now is as great as anything that Mr. Obama is likely to do his entire presidency," said Michael O'Hanlon of the Brookings Institution. "We've got to try…and cajole and convince [Afghan] President Karzai to make some positive steps forward at this moment of leverage."
Kerry, who met with Karzai five times over five days prior to the announcement of a runoff, took a dramatic walk with the Afghan president around a Kabul mosque Tuesday. He apparently told Karzai of his own experiences in the 2004 U.S. presidential election, saying "Sometimes there are tough things and you just have to move on."
ABC News' George Stephanopoulos and Sunlen Miller contributed to this report.