FRANKFURT — Once, the merger of two iconic European companies might well have been derailed by regional political rivalries. But in the case of a deal between Siemens and Alstom, those concerns have receded in the face of a larger threat: China.

The proposed merger of Europe’s two largest train makers, one German and one French, demonstrated on Wednesday that economic imperatives are pushing the Continent together even as populist politicians try to pull it apart.

Siemens, a German electronics and engineering giant, and France’s Alstom, a maker of the high-speed TGV, said late Tuesday that they will merge their units that make trains, streetcars and signaling systems. The deal is backed by the French government, and the two companies provided details of the deal the following day.

The new company, to be called Siemens Alstom, is a response to intensifying competition from China Railway Rolling Stock Corporation, the state-backed train maker that has been winning contracts in the United States and emerging markets where mass transit is a fast-growing business.