Obama visits wounded Congresswoman Giffords

President Barack Obama visited wounded Representative Gabrielle Giffords to begin an emotional trip to Arizona as political leaders condemned the deadly shooting spree in Tucson.

Obama's motorcade carried him to University Medical Centre shortly after he landed in Tucson to address a memorial service for the six killed and 14 wounded by a gunman who opened fire while Giffords met voters last Saturday.

"The president wanted to begin this solemn trip by stopping first at the hospital where Congresswoman Giffords and others continue to recuperate," White House spokesman Robert Gibbs told reporters.

Obama was to address the memorial service later in an appearance in which he was expected to call on US citizens to unite regardless of political divisions and offer comfort to the families of the victims.

He was expected to speak for up to 18 minutes, and devote a significant portion of his remarks to the memory of the victims.

"He'll also reflect on how all of us might best honour their memory in our own lives," Gibbs said.

In Washington, the House of Representatives condemned the shootings that gravely wounded Giffords, denouncing the "horrific attack" that has left lawmakers worried about their own security.

Member after member of the House spoke of their respect for Giffords, a third-term Democrat who is in critical condition with a bullet wound to the head, which she suffered while meeting with constituents at an outdoor event.

House Speaker John Boehner, struggling to hold back tears, opened a day of speeches on the resolution saying, "We are called here to mourn an unspeakable act of violence ... these are difficult hours for our country."

The resolution replaced on the House schedule what originally had been set as a day for voting to repeal Obama's landmark healthcare reform law.

Besides honouring Giffords and the other victims, the resolution applauded the bravery of those at the scene on Saturday who may have prevented more loss of life.

Jared Lee Loughner, 22, has been accused of firing at Giffords and others gathered in a Tucson parking lot where the congresswoman was hosting an event for constituents.