It's been a decade since the Iraq war first began, and a clear majority  of Americans still say the fight was not worth its costs, according to a new Washington Post-ABC News poll. Democrats and Republicans continue to disagree about whether the invasion made the United States any safer.

The public soured on Iraq years ago but is now similarly downbeat about the war in Afghanistan, which President Obama once portrayed as the more worthwhile conflict. Some 58 percent of the poll's respondents say Iraq was not worth the fight; 56 percent say so about Afghanistan.

The costs of those wars have been steep. The U.S. military has suffered more than 6,600 casualties in the wars since 2003. And beyond the considerable human toll, the political consequences were a bitter pill for President George W. Bush. His approval ratings declined in his second term just as rapidly as support for the war, never to rebound.

In the early stages of the Iraq invasion, more than nine in 10 Republicans and seven in 10 independents said the effort was worth the costs. Just half of Democrats said it was worthwhile. Today, support for the war is lower across the board. Among Republicans, 57 percent see the war as worth fighting; just 35 percent of independents and 27 percent of Democrats agree.

Today, opinions of the war in Afghanistan are almost identical to those about Iraq. Those saying Afghanistan has been "worth it" have ticked up nine percentage points since last year, to 39 percent. But 56 percent still says the effort was not worth it.

Afghanistan had been a more popular war than Iraq. From 2007 to mid-2009, at least half the public said the war was worth the sacrifice. During that same period, about six in 10 said Iraq was not worth it.

Support for the war in Afghanistan turned south in 2010, with the sharpest falloff among Republicans. From 2007 until mid-2009, more than seven in 10 Republicans said the war was worth it. But by the end of 2010, only half of Republicans said it was worthwhile. Opinions among Democrats and independents have been more stable over the seven years of Post-ABC polls on Afghanistan.

Deep reservations about both wars appear to be closely tied to security considerations. Fewer than half of respondents say the Iraq war has contributed to the long-term security of the United States. And a bare majority say so about the Afghanistan war.

More than six in 10 Republicans say each war has made the country safer. Democrats evaluate each war a little differently, but are less apt than Republicans to see a security benefit. A bare 51 percent majority of Democrats say the Afghanistan war has contributed to long-term U.S. security. But only 41 percent of Democrats say the Iraq war delivered the same.

The authors are pollsters with Capital Insight, the independent polling group of Washington Post Media. Polling director Jon Cohen contributed to this report.