WASHINGTON — President Obama's speech from the Oval Office was intended to jump-start his political prospects in November's congressional elections by explaining again his objectives in Iraq and Afghanistan. It was of questionable benefit.

Use of that august venue for the second time in his presidency obviously was intended to give particular gravitas to the attempt. But the only limited and tentative optimism he could convey in the face of reality challenged the wisdom of his making the speech at all.

His formal declaration of "the end of our combat mission in Iraq" was a distinction that could be taken to suggest that the war there is "over." But that is belied by the fact that deaths and casualties, while greatly reduced, are continuing.

In calling this juncture a "historic moment" and a "milestone," Obama argued that "the Americans who have served in Iraq completed every mission they were given." He cited toppling the Saddam Hussein regime, countering the insurgency and enabling the Iraqis to "hold credible elections that drew a strong turnout."

Obama prudently declared no "Mission Accomplished" akin to the premature boast of the previous administration. But in pointing to the end of U.S. combat operations, he only reminded his countrymen that the American involvement goes on.

That the U.S. forces have been reduced by nearly 100,000 to only 50,000 "non-combat" troops isn't likely to reduce materially the American public's anxiety and impatience. In their training role to fight the insurgents, the troops are certain to take more casualties.

The president's claim that he has delivered on his 2008 campaign promise to wind down the war won't resonate much, either, with an American public that tells pollsters in increasing numbers that they don't believe the war was worth fighting and that they want it to end — period.

In Obama's only reference to former President George W. Bush, he mentioned their disagreement over the Iraq war "from the outset," with no mention that he also opposed Bush's troop surge, which is credited by many now as having made the end of the U.S. combat mission possible. He rather gratuitously testified as to Bush's "support for our troops" and "his love of country and commitment to our security."

Most importantly, Obama repeated that, in accord with the agreement Bush struck with the Iraqi caretaker government, "all U.S. troops will leave by the end of next year," to be replaced by diplomats and other civilians working toward governmental stability in the country.

Regarding Afghanistan, Obama always has said it was a war of necessity in the wake of the 9/11 attacks by terrorists harbored there. He reaffirmed that the mission remains to "disrupt, dismantle and defeat al-Qaida, while preventing Afghanistan from again serving as a base for terrorists."

In so saying, the president drew the same distinction that emerged from his long review with his military leaders last winter. He made clear then that his own focus was not nation building in either Iraq or Afghanistan, while justifying his controversial troop surge in the latter.

This determination to limit the American purpose and obligation in Afghanistan is at the core of Obama's continued insistence that he will start withdrawing American troops there next summer. His only leeway in the speech was, as the generals have urged, to say "the pace of our troop reductions will be determined by conditions on the ground."

In all this remains Obama's broad 2008 campaign pledge actually to "end" both wars, dictated particularly now by the need to redirect the nation's resources and treasure toward the dire economic plight at home that imperils his presidency.

In the wake of the 9/11 attacks, the American people understood and bought into the Afghanistan mission as what Obama says today it is — retaliating against and eliminating the al-Qaida perpetrators. It was not to build democracy in the Middle East, no matter how desirable that might be.

Pivoting from that grandiose mission and getting back to dealing with America's own pressing problems is Obama's challenge. His speech was an effort to clarify and justify it, and it probably was only partially successful.

Jules Witcover's latest book, on the Nixon-Agnew relationship, is "Very Strange Bedfellows."