By David Latona and Silvio Castellanos

SEVILLE, Spain (Reuters) -Activists marched in blistering heat through southern Spain's Seville on Sunday, calling for debt cancellation, climate justice and taxing the super rich on the eve of a UN summit on financing development that critics say lacks ambition and scope.

The four-day meeting - held once every decade - promises to take on poverty, disease and climate change by mapping out the global framework for development. But the United States' decision to pull out and wealthy countries' shrinking appetite for foreign aid have dampened hopes that the summit will bring about significant change.

Greenpeace members carried a float depicting billionaire Elon Musk as a baby wielding a chainsaw, seated atop a terrestrial globe. Others held up banners reading "Make Human Rights Great Again", "Tax justice now" or "Make polluters pay".

Beauty Narteh of Ghana's Anti-Corruption Coalition said her group wanted a fairer tax system and "dignity, not handouts".

Sokhna Ndiaye, of the Africa Development Interchange Network, called on the public and private sectors to be "less selfish and show more solidarity" with developing countries.

Hours earlier, however, Spanish Prime Minister Pedro Sanchez said that "the very fact that this conference is happening while conflict is raging across the globe is a reason to be hopeful".

Speaking at an event by non-profit Global Citizen, Sanchez reiterated Madrid's commitment to reach 0.7% of GDP in development aid and urged other countries to do the same.

Jason Braganza, executive director of pan-African advocacy group AFRODAD who took part in the year-long negotiation on the conference's final outcome document, said countries including the U.S., the European Union and Britain had obstructed efforts to organise a UN convention on sovereign debt.

"It's a shame these countries have opted to protect their own interests and those of creditors over lives that are being lost," he added.

(Reporting by David Latona and Silvio Castellanos; Editing by Andrea Ricci)