US President Barack Obama said Monday on Memorial Day that troops are coming home after a decade of war and must be respected, with no repeat of the "national shame" that greeted many Vietnam veterans.

In two speeches to mark the annual commemoration of fallen and missing soldiers, Obama said US troops were no longer fighting in Iraq and that he was "winding down" America's war in Afghanistan.

As a result, he said, the focus must now shift to ensuring a future for those returning from the battlefield.

"For the first time in nine years, Americans are not fighting and dying in Iraq," Obama said after laying a wreath on the Tomb of the Unknowns, in Arlington National Cemetery just outside Washington.

"We are winding down the war in Afghanistan and our troops will continue to come home," he added at the final resting place for US war dead and veterans, which features many fresh graves from Iraq and Afghanistan.

"After a decade under the dark clouds of war, we can see the light of a new day on the horizon."

After sweeping to power in 2008 partly owing to his promise to end the war in Iraq, Obama followed through by bringing the final US soldiers home last year.

Obama is highlighting that honored promise, and a plan to get US combat troops out of Afghanistan by the end of 2014, to bolster his leadership credentials as he faces reelection in November.

But the president, who also serves as commander-in-chief of US forces, noted that for relatives of the fallen, the end of America's foreign wars may hold little consolation.

"Especially for those who have lost a loved one, this chapter will remain open long after the guns have fallen silent," Obama said.

A few hours later, in a speech at the Vietnam War Memorial in Washington, he reached out to veterans of that conflict, which spiraled out of control in the 1950s and claimed the lives of tens of thousands.

"One of the most painful chapters in our history was Vietnam -- most particularly, how we treated our troops who served there," Obama told a crowd at the Vietnam wall, where the names of 58,000 soldiers, airmen, sailors and Marines are engraved.

"You were often blamed for a war you didn't start, when you should have been commended for serving your country with valor. You were sometimes blamed for misdeeds of a few, when the honorable service of the many should have been praised," he said.

"You came home and sometimes were denigrated, when you should have been celebrated. It was a national shame, a disgrace that should have never happened. And that's why here today we resolve that it will not happen again."

Obama said the US Department of Veterans Affairs aimed to ensure that those who survive conflict return home and gain the support needed to lead successful civilian lives.

The US is "helping hundreds of thousands of today's veterans go to college and pursue their dreams" through the GI Bill, the president said as he praised Vietnam veterans for leading the effort.

"Because of you, across America, communities have welcomed home our forces from Iraq. And when our troops return from Afghanistan, America will give this entire 9/11 generation the welcome home they deserve," Obama added.

Obama's Republican opponent in November's presidential election, Mitt Romney, also issued a message, as he joined Vietnam war hero and defeated 2008 Republican candidate Senator John McCain to mark Memorial Day in San Diego.

"A lot of young Americans are risking their lives in distant battlefields today," Romney said in the statement.

"Memorial Day is a day to give thanks to them, and to remember all of America's soldiers who have laid down their lives to defend our country."