1. The Bazooka. The EU's Instrument Against Economic Coercion (ACI) is designed specifically to target countries that try to use trade threats against an EU member. This can involve import and export restrictions, punitive tariffs and preventing US companies from participating in public procurement. It requires a qualified majority in the Council and takes several months before it comes into force, but is seen as a powerful weapon - which, however, risks escalating the conflict further.
2. Hunt down US companies. A more surgical instrument is to use existing EU laws to target US companies, such as tech giants, or to limit imports of certain agricultural goods. For example, the EU could claim that certain companies are unfairly benefiting from state aid, or that certain products do not meet EU health standards.
3. Stop the tariff deal. Last summer, the EU and the US agreed on an EU-US tariff deal, in which the EU accepted 15 percent tariffs on exports to the US, while the EU eliminated tariffs on US goods. The European Parliament has not yet ratified that agreement.
4. Strengthen defense. Denmark and other countries could increase their military presence, to try to calm Trump, who has claimed that Denmark can do nothing to protect the island against Russia or China. Eva Hagström Frisell, research director at the Swedish National Defense Research Institute FOI, says that this could involve more ships, surveillance drones and air surveillance.
5. Invite the Americans. One possibility to make Trump appear victorious is to encourage the US to increase its own military presence, or to invite companies to explore Greenland's natural resources, while at the same time preventing any Russian and Chinese companies.
"Then he could say that 'we got what we wanted' within the framework of existing agreements," says Hagström Frisell.
6. Delay. The EU can also choose a wait-and-see attitude, or try to delay and let diplomacy fizzle out.
"You can try to normalize the conversation and remove it from social media," says Neil Melvin, head of international security at the think tank RUSI.
7. Hold an independence referendum. Greenlanders could vote on independence. If they vote yes, the country could choose to become part of the United States. Neil Melvin draws parallels to the Scottish independence referendum in 2014, which largely took the issue off the table.
"I think that in that case it would be an extension of the delay option," Melvin says.
8. Divide responsibility. Introduce some form of joint governance over Greenland, without the island becoming a formal part of the United States.
"If you believe in diplomacy and international law, you might be able to do it. But for a real estate agent, it might be too complicated," says Melvin.
US President Donald Trump has threatened eight European countries, including Sweden, with 10 percent tariffs starting February 1.
Trump's tariff threat comes after Sweden and other countries - all NATO members - protested against Trump's increasingly aggressive demands for the US to take over Greenland, and also initiated a joint military exercise in Greenland.
The governments of the EU countries - who have called for an extraordinary summit on Thursday - are now discussing possible countermeasures.
Among other things, there is a proposal for EU tariffs on US goods worth around SEK 1,000 billion. It may also be possible to introduce more extensive trade restrictions, such as blocking US companies from public procurement in the EU.
Trump has said that the 10 percent tariffs will be raised to 25 percent in June if there is no deal on Greenland by then.
