WASHINGTON - Confronting an inherited and faltering war, President Barack Obama plans to deploy thousands more military and civilian trainers to Afghanistan by the fall on top of the 17,000 combat troops he has already ordered, senior administration officials said Thursday.

Obama's war strategy, which will he announce Friday, includes no timeline for withdrawal of troops. The war began more than seven years ago.

The sources said Obama's goal is to stabilize Afghanistan and eliminate terrorist havens that have taken root in Pakistan. They said the plan is built around benchmarks that will allow the president and Congress to check whether the investment of more U.S. people and aid is working.

Three senior administration officials described Obama's plan on condition of anonymity.

Obama plans to send 4,000 more U.S. troops whose mission will be to train and expand the Afghan army to take the lead in counterterrorism and counterinsurgency. The president also plans to send in hundreds more U.S. civilians to help the people of Afghanistan rebuild their country.

More broadly, the new strategy links Afghanistan and Pakistan as one integrated challenge. Obama will support legislation that aims to pump billions of dollars aid into Pakistan, considered to be the primary haven for terrorists since U.S.-led forces toppled the Taliban government in Afghanistan in 2001.

Obama called Afghan President Hamid Karzai and Pakistani President Asif Ali Zardari to brief them on his plans.

"He made it very clear there are no blank cheques," one administration official said.