Amazon is facing pressure from thousands of employees to take a stronger stance on climate change.

The employees signed an open letter, calling on the e-commerce giant to adopt a plan to phase out the use of fossil fuels. The workers also want Amazon to end partnerships with oil and gas companies, and to play a more active role in telling local and federal governments to reduce carbon emissions.

"Amazon has the resources and scale to spark the world's imagination and redefine what is possible and necessary to address the climate crisis," reads the letter, which is signed by more than 4,000 workers.

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Wednesday's letter seeks to build support for a shareholder proposal that demands Amazon release a plan to address climate change. According to the protesting workers, the proposal is on track for a shareholder's vote next month, but company leadership is preparing to oppose it.

Amazon's current goal is to control the company's carbon footprint over the next decade, not completely eliminate it. "Our vision to make all Amazon shipments net zero carbon, with 50 percent of all shipments net zero by 2030," a company spokesperson told PCMag.

But the protesting workers say this isn't enough. "Given Amazon's rate of growth, reaching 50 percent net-zero shipments by 2030 could still be an increase in emissions compared to today," their letter reads.

The protesting works also oppose an Amazon effort to help fossil fuel companies streamline their IT systems to expand oil and gas mining. Amazon's clients include BP, Shell, and GE Oil and Gas, among others. "To avert catastrophic warming, the science is clear: we must keep fossil fuels in the ground," their letter adds.

In response, Amazon told PCMag that the company's long-term goal is to power the company's global infrastructure using only renewable energy. When this might be achieved Amazon didn't say, but the company plans to unveil new sustainability projects this year.

"In operations alone, we have over 200 scientists, engineers, and product designers dedicated exclusively to inventing new ways to leverage our scale for the good of customers and the planet," the company added.

Amazon's past sustainability projects include creating wind and solar farms to power some company buildings. But on the shipping front, the company recently bought a fleet of 20,000 delivery vans, which reportedly run on diesel.

Wednesday's letter is the latest employee-led protest effort at a major tech company. Last year, Amazon workers spoke out against the company's plans to sell facial-recognition systems to government agencies over surveillance fears. A separate shareholder proposal is slated to go up for a vote next month, demanding Amazon stop sales to government clients until the surveillance risks have been addressed.

This article originally appeared on PCMag.com.