China will boost spending on U.S. products in exchange for rolling back of some tariffs under an initial trade deal signed by the world's two largest economies Wednesday, defusing an 18-month row but leaving numerous thorny issues unresolved.

Beijing and Washington touted the "phase one" agreement as a step forward after months of stop-start talks, and investors greeted the news with relief. Even so, there was skepticism over whether the U.S.-China trade relationship was now firmly on the mend.

The deal fails to address the structural economic issues that led to the trade conflict, does not fully eliminate the tariffs that have slowed the global economy, and sets hard-to-achieve purchase targets, analysts and industry leaders said.