The first incident, killing 10 American troops, occurred in the western part of the country after their helicopter went down.

Four more troops died when their helicopters collided in southern Afghanistan.

In his remarks, the president paid tribute to the families of the 14 killed U.S. troops.

"While no words can ease the ache in their hearts today, may they find some comfort in knowing this: like all those who give their lives in service to America, they were doing their duty and they were doing this nation proud," he said.

"They were willing to risk their lives, in this case, to prevent Afghanistan from once again becoming a safe haven for al- Qaida and its extremist allies," Obama added.

The growing casualty toll is believed to be a key reason why public support for the Afghan war wanes in the United States, which makes sending more troops to Afghanistan a politically risky decision.

That partially explains why Obama took great cautions in the approach to make such a decision.

NO CLEAR TIMELINE FOR DECISION

Before flying into Jacksonville, Obama met his national security team to discuss U.S. strategy in Afghanistan and Pakistan for the sixth time in a month.

But there is still no clear timeline for when a decision could be reached.

White House spokesman Robert Gibbs said the decision will be made in "coming weeks," a line the Obama administration repeated for weeks.

The remarks sounds a retreat from a statement he made on last Wednesday, when he told reporters that the decision on whether to send more troops to Afghanistan could come before the Nov. 7 Afghanistan runoff election.

Some analysts said the time frame for Obama to make such a decision is tight, since he will soon embark on a long trip to Asia starting Nov. 12.

However, recent developments, including new U.S. casualties and Afghan political turmoil, could add more complications into the president's decision-making process.