Chances looked good for the resolution of a years-in-the-making investment agreement between China and the European Commission before the end of the year. This week, that changed.

In the span of days, reports of an emerging consensus gave way to news that negotiators had hit snags, as European officials voiced concern about forced labor in China and a senior aide to President-elect Joe Biden appeared to urge Europe to pump the brakes.

China and Germany are pushing the deal, which would make it easier for European and Chinese companies to invest in each other’s economies. But voices on both sides of the Atlantic are questioning whether this is the right time for Europe to deepen ties with Beijing.

The back and forth says much about how central — and how fraught — the issue of relations with China has become, both within the European Union and between Europe and the United States.

Within the E.U., there is growing unease about Beijing’s human rights record and role in international affairs, but little agreement on what to do about it.

Biden has promised to re-engage with Europe and to rally allies to respond to an increasingly assertive China. The timing and terms of that effort are not yet clear.

Against this backdrop, the fate of the investment pact is seen as an early signal of tensions set to play out in years to come, on issues such as trade, tech regulation and climate change.