A new pact between the U.S. and China to tackle greenhouse-gas emissions has raised the question: Could India be next to set targets? After all, the two most-populous countries in the world have long acted together in climate-change talks. Indian officials say, however, that Beijing’s deal has only highlighted the vast gap between a surging China and an India struggling to catch up. India appears unwilling to take steps that could burden its economy as it strives to build modern manufacturing industries. Beijing and New Delhi used to join forces to stave off pressure from developed nations to curb emissions, arguing that high carbon-dioxide levels are a problem that now-wealthy, industrialized nations created over many years and not something developing countries should be expected to solve.