By Steve Schifferes BBC News Online Washington correspondent

All across the capital, churches, synagogues and mosques held services of remembrance.

We've got to fulfil our destiny and the character of people as explorers and adventurers Senator Bill Nelson, former astronaut

President George W Bush and the First Lady attended the small St John's Episcopal Church directly opposite the White House, where they heard their local minister praise the courage of the Columbia crew.

"God's heart is more heartbroken than our own, and I believe they're already resting," the Reverend Luis Leon said as he asked parishioners to hug each other as the names of the seven astronauts were read out.

The President attended church across from the White House

At the Johnson space flight centre in Houston, the headquarters of the manned space programme, hundreds of people left floral tributes outside the main gate, and some lit candles and said prayers.

And in the Grace Community Church in Houston, where two of the astronauts, Rick Husband and Mike Anderson, had worshipped, the pastor said there could be no triumph without tragedy.

Politics suspended

The shuttle disaster has led to the suspension of politics as usual, as the talk shows replaced their political guests with astronauts and Nasa administrators in specially extended additions.

Mankind is led into the darkness beyond our world by the inspiration of discovery and the longing to understand. Our journey into space will go on President George W Bush

In Iowa, Senator Joe Lieberman, a leading candidate for the Democratic nomination for president in 2004, postponed his first trip into the state which could be crucial to his chances, saying it would be inappropriate "in this time of national tragedy."

Sadness over the tragedy has temporarily suspended worries over the impending crises in Iraq and North Korea, with Secretary of State Colin Powell due to present US evidence on Iraq to the Security Council on Wednesday.

And there was little talk of President Bush's $2.2 trillion Federal budget, due to be presented to Congress on Monday.

People were shocked by the disaster

Nasa administrator Sean O'Keefe denied reports that budget cutbacks had compromised safety on the shuttle programme.

But advocates of space exploration said they hoped the tragedy would cause America to renew its commitment to Nasa, and even give it a new purpose, such as sending a man to Mars.

America's destiny

Senator Bill Nelson, a former astronaut, said: "We've got to fulfil our destiny as... explorers and adventurers and go to Mars and go back to the Moon."

Senator Kay Bailey Hutchison of Texas, who said Nasa's budget had been cut by 40%, argued that: "We cannot be second-place to anyone in the world with the technological advances that we can have by going into space research."

It is a sign of the prestige of the space programme that three astronauts have become Senators, including John Glenn, the first American to orbit the Earth.

And it was left to America's most famous astronaut to make the case that it was the thirst for exploration and discovery that had made the United States a great nation, from the first time settlers arrived on the American continent and started to move West.

The former Senator told NBC's Meet the Press programme: "It was the quest for new knowledge... that has led our nation to exceed the whole world... These people gave their lives just like any of our explorers in history."

And it appears to be a sentiment shared by President Bush who, like his father, has a deep and abiding interest in space travel.

When he spoke soon after the tragedy, the President said:

"Mankind is led into the darkness beyond our world by the inspiration of discovery and the longing to understand. Our journey into space will go on."

It was a sentiment that echoed the words of President John F Kennedy, who launched the space race in l961 with a ringing call for Americans to tackle "the new frontier."

Finding that common purpose again in the face of the tragedy will be the biggest challenge for Americans.