Barack Obama has claimed victory in the race for the Democratic Party's nomination for the US Presidency.Mr Obama would be the first black presidential nominee for a major US party and said he would "bring a new and better day to America".The 46-year-old Illinois senator, with his message of hope and change for the US, effectively clinched the nomination on the final day of one of the closest and most expensive primary seasons in memory."Tonight we mark the end of one historic journey with the beginning of another, a journey that will bring a new and better day to America," he said."Because of you tonight I can stand here and say that I will be the Democratic nominee for president of the United States of America."Speaking in St Paul, Minnesota, Mr Obama also paid tribute to his rival Hillary Clinton, who had just stressed her power and influence in her own speech, and said she made him a "better candidate".Mr Obama told a crowd of around 20,000 supporters: "At this defining moment for our nation, we should be proud that our party put forth one of the most talented, qualified field of individuals ever to run for office."He said his rivals for the party's nomination were "leaders that America will turn to for years to come"."And that is particularly true for the candidate who has travelled further on this journey than anybody else," he said."Senator Hillary Clinton has made history in this campaign, not just because she is a woman who has done what no woman has done before, but because she is a leader who has inspires millions of Americans with her strength, her courage and her commitment to the causes that brought us here tonight."Mr Obama said he and Mrs Clinton "certainly had our differences this past 18 months" but praised her desire to improve the lives of ordinary Americans."And you can rest assured that when we finally win the battle for universal healthcare in this country, and we will win that fight, she will be central to that victory," Mr Obama said."Our party and our country are better off because of her and I am a better candidate for having had the honour to compete with Hillary Rodham Clinton."For her part, Mrs Clinton showed no sign of suspending her presidential campaign in a speech which was widely seen as the former first lady flexing her power and influence.But she did say that the Democratic Party was "stronger and more vibrant" as a result of Mr Obama's campaign.Speaking at Baruch College in her home city of New York, the former first lady said Mr Obama had "inspired so many Americans to care about politics".Mrs Clinton swiftly signalled her interest in joining his ticket as a potential vice president.She told cheering supporters: "Now the question is, 'Where do we go from here?' And given how far we've come, and where we need to go as a party, it's a question I don't take lightly."This has been a long campaign and I will be making no decisions tonight."