VINEYARD HAVEN, Mass. — With his Oval Office speech Tuesday night, President Barack Obama will signal a shift in America's focus from the Iraq War to the war in Afghanistan, his spokesman said today.

Administration officials have portrayed the speech as an important pivot point from a war that candidate Obama said should never have been fought to a conflict that President Obama sees as vital to the nation's security.

Previewing the speech as Obama vacationed on Martha's Vineyard, Deputy Press Secretary Bill Burton said Obama also wants to thank U.S. troops who've fought bravely in Iraq. With the formal U.S. combat mission at an end, troop strength in Iraq this week dropped below 50,000 for the first time since the 2003 U.S.-led invasion. Many of those troops will remain in a backup and training role.

Before his White House speech, Obama will fly to Fort Bliss in Texas on Tuesday to deliver his thanks in person to troops returned from Iraq.

Burton said Obama will use the occasion to speak "directly with the American people about what our mission is in Afghanistan (and) the fact that more of our efforts and focus are now on fighting al-Qaida in Afghanistan."

By The Associated Press