TEHRAN — The French energy giant Total has agreed to invest $1 billion in Iran to develop a huge offshore gas field, Iranian news media reported on Sunday.

The agreement, the largest by a Western energy company in Iran since the 2015 deal to curb Tehran’s nuclear program, had been delayed in February as Total waited to see how the Trump administration’s policy toward Iran would proceed.

President Trump has spoken out against the multilateral nuclear agreement, and his antipathy toward the pact and talk of further sanctions has raised concerns among foreign energy firms looking to invest in Iran. But the administration has approved sanction waivers allowing deals under the nuclear agreement.

Total will take a 50 percent stake in the development of the 11th phase of the South Pars gas field, investing $1 billion into the $4.8 billion project, the semiofficial Tasnim news agency reported on Sunday. The other partners are the China National Petroleum Corporation and the Iranian company Petropars.