By PHILIP ELLIOTT

WASHINGTON — President Barack Obama’s chief spokesman said today that he will make a decision “within days, not weeks,” on how many additional troops to send to Afghanistan, and when.

White House press secretary Robert Gibbs made the observation in a chat with reporters today aboard Air Force One as Obama and his family flew back to the Washington area after a long weekend in his hometown of Chicago.

The president, his wife and daughters arrived at the military base just outside Washington at midday today. His family had left for Chicago on Friday aboard Air Force One. Among items topping Obama’s agenda this week is signing into law the $787 billion economic stimulus plan that Congress passed last Friday.

Obama has been widely believed likely to send fresh forces to the Afghan battle even as a wide review of U.S. strategy and goals there gets fully under way.

Defense Secretary Robert Gates had told a Pentagon news conference last week that Obama “will have several options in front of him.” Gates suggested, as have other officials, that the ground commander in Afghanistan would eventually get all the forces he has asked for, but no more.

Lt. Gen. David McKiernan wants more fighting forces and support troops such as helicopter crews to push back against the Taliban in Afghanistan’s increasingly dangerous south and eastern regions.

An opponent of the “surge” of U.S. forces that is now credited with turning around the Iraq war, Obama has taken a cautious approach to the addition of forces in Afghanistan. He is expected to initially approve only part of a military request for as many as 30,000 forces this year, while military and civilian advisers revamp U.S. war goals.

While in Chicago, the first family did not have a public schedule. The president played basketball with friends, visited the gym and got a haircut. Barack and Michelle Obama celebrated Valentine’s Day with a dinner at Oprah Winfrey’s personal chef’s restaurant on Saturday.

It was Obama’s first significant break since taking office on Jan. 20.

Obama won’t be in Washington long; he heads to Denver, Colo., Arizona and Canada this week and he plans to sign the stimulus legislation in Denver.