WASHINGTON — As the United States braces for an especially bloody summer fighting season in Afghanistan, President Obama inched closer this week to allowing American forces to once again directly battle the Taliban, loosening restrictions on airstrikes and on ground combat in support of Afghan forces, the administration said on Friday.

The president’s decision to expand the military’s mission just seven months before he leaves office signaled just how far the United States remains from achieving his goal of ending the American military role in Afghanistan.

Under the new rules, airstrikes will no longer have to be justified as necessary to defend American troops. United States commanders will now be allowed to use air power against the Taliban when they see fit, Pentagon and administration officials said. American forces will also be permitted to accompany regular Afghan troops into combat against the Taliban.