(Ebru News/AP) Senators Barack Obama and Hillary Rodham Clinton's battle for the Democratic presidential nomination shifted on Tuesday from Mississippi, where Obama won on Tuesday, to Pennsylvania where she hopes to win. The campaign rhetoric was dominated by talk of jobs and trade.

Senator Barack Obama, Democratic presidential hopeful said:
"Trade is important as part of that economy and we can't shrink from that challenge, but I am going to make sure that our trade deals have strong labour and environmental protections to help keep jobs here in Pennsylvania."

Senator Hillary Rodham Clinton said:"In Ohio we've just finished a campaign talking about NAFTA (North American Free Trade Agreement) and trade. I have said I will renegotiate NAFTA. I will make sure it reflects what we have learned over the last 14 years.

As he opened his campaign for the Pennsylvania primary six weeks away, Obama promised on Tuesday to encourage trade, but to enact new safeguards for workers and the environment.

Senator Barack Obama, Democratic presidential hopeful said:"And that is why as President I will invest 150 (b) billion dollars (75 (b) billion pounds) over ten years in establishing a green energy sector that will create up to five (m) million new jobs, including jobs here in Pennsylvania."

Speaking at a rally in Pennsylvania, Clinton blasted Obama over recent statements he made but then had to back away from

Senator Hillary Rodham Clinton, Democratic presidential said:".... I gotta tell you, there is a big difference between talk and action, but if you're going to talk, then you ought to mean what you say so that people can count on it."

In the overall race for the nomination, Obama has 1,596 delegates, and Clinton has 1,484,

It takes 2,025 delegates to secure the Democratic nomination at the party's national convention in Denver this summer