BRUSSELS — The European Union agreed Thursday on a set of rules for allowing non-member countries like the United States or Britain to take part in dozens of potentially lucrative defense projects.

So far, 47 projects have been launched under the EU's scheme of Permanent Structured Cooperation, or PESCO. They range from the construction of command centers and anti-mine systems to developing new drones and upgrading aircraft and tanks. Each project is run by small groups of EU member countries.

President Donald Trump threatened retaliation last year if the U.S. was not permitted to take part. Britain also is keen to be involved in the defense projects even though it officially left the EU this year, and questions remain over whether it will reach an agreement on future relations with the bloc.

But EU member countries hailed Thursday's agreement on the rules for PESCO participation and said it "will enhance the EU's strategic autonomy and strengthen its capacity to act as a security provider, together with its partners."

The deal allows non-EU governments to apply to join a particular project. Participation would be judged on a number of political considerations. For instance, the countries would have to share the values on which the EU is founded and not contravene the bloc's defense interests.

But applicants would also have to bring substantial added value to the particular project and should not impose any restrictions on the way it would be used in Europe. In addition, the countries must have a security of information agreement with the EU.

The countries in charge of the project concerned would then request a vote among all 25 nations involved in the PESCO scheme. The application must be accepted unanimously.

EU officials refused to be drawn on whether the U.S. would qualify. Trump abandoned the Iran nuclear deal, which the Europeans consider to be important to their security, and also imposed steel and aluminum tariffs on Europe for what he said were reasons of national security.

The EU has routinely criticized Turkey for reneging on European values even as the country still insists that it wants to join the world's biggest trading bloc.