European officials are preparing to introduce ambitious legislation designed to wean one of the world’s biggest and most polluting economies off fossil fuels far more quickly than other nations have pledged to do. The proposals could include phasing out coal as an electricity source as well as imposing tariffs on polluting imports — an idea with the potential to set off global trade disputes.

The European Commission’s package of around a dozen legislative proposals, expected on Wednesday, is designed to swiftly reduce the emissions of planet-warming gases and meet an ambitious climate goal, already enshrined in law: The 27-nation bloc has said it will cut its emissions of greenhouse gases by 55 percent by 2030, compared to 1990 levels.

The legislation is expected to be in sharp contrast to vague aspirations by various other countries to neutralize their emissions by midcentury. “It’s not just a big promise,” said Jennifer Tollmann, a Berlin-based analyst for E3G, a research and advocacy group that works on climate policy.

The proposals, known as “Fit for 55,” are just that — proposals. They will take many months to negotiate among the 27 member countries and the European Parliament before becoming law. And they will most certainly invite scrutiny of Europe’s own reliance on extracting and burning fossil fuels in its own territories, from oil and gas drilling in the North Sea to coal mining in countries like Germany and Poland.

The most contentious element is something called a border carbon adjustment tax. It would impose tariffs on the greenhouse gas emissions associated with products imported from outside the European Union and, in effect, would protect European companies from goods made in countries with less-stringent climate policies. Among the products that it could target, according to a draft leaked in June, are steel, cement, iron and fertilizers.

This carbon border tax could not only shake up global trade and invite a dispute over protectionism in the World Trade Organization, it could also create new diplomatic fault lines ahead of international climate talks taking place in Glasgow in November.