ROME ― The U.S. is keeping a close eye on a newly formed European Union joint defense agreement to ensure that European members are not distracted from their NATO commitments.

Katie Wheelbarger, principal deputy assistant secretary for international security affairs, told reporters travelling with Secretary of Defense Jim Mattis that the issue of fitting the new group and NATO together would be part of Mattis’ discussion with defense ministers this week in Europe.

“We are supportive of it, as long as it is complimentary to and not distracting from NATO’s activities and requirements,” Wheelbarger said. “We don’t want to see E.U. efforts pulling requirements or forces away from NATO and into the E.U.”

The E.U. launched the Permanent Structured Cooperation on Security and Defence (PESCO) in late 2017, so the project is still in its early days. Unlike previous proposals for EU joint defense, PESCO comes with regular assessments to make sure countries are hitting their pledged goals for investments in capability or capacity. Countries that fail to meet their commitments could be removed from the group.

The countries involved ― Austria, Belgium, Bulgaria, Czech Republic, Croatia, Cyprus, Estonia, Finland, France, Germany, Greece, Hungary, Italy, Ireland, Latvia, Lithuania, Luxembourg, the Netherlands, Poland, Portugal, Romania, Slovenia, Slovakia, Spain and Sweden ― overlap with the NATO nations, with some key differences.

Austria, Cyprus, Finland, Ireland and Sweden are non-NATO countries, while PESCO excludes Canada, the U.S. and the U.K., three members of NATO not based on the continent that often drive the alliance conversation; instead, PESCO is being driven by France, Germany, Italy and Spain.

Roberta Pinotti, Italy’s defense minister, wrote in an editorial for Defense News that PESCO “might represent the best and, right now, the only possible response to the challenges to international security and Europe’s defense.”

“We need new joint investment in which the EU has a key financial but also political role — new programs must reflect European needs and must be seen by all as intrinsically European,” Pinotti wrote. “This does not mean cutting back national responsibilities and commitments, but throwing them behind the more ambitious project of protecting Europe’s strategic interests.

The list of potential PESCO projects are still being created, but the creation of a new defense funding mechanism ― under which NATO countries could pool resources for, as Pinotti put it, “intrinsically European” needs and not necessarily spend that funding how NATO would like them to ― has the U.S. keeping a close eye on proceedings.

Supporters of PESCO have argued that the group will not conflict with NATO. In November, E.U. foreign policy chief Federica Mogherini said PESCO would be able to act where NATO could not, as it would bring a whole-of-government approach to issues, such as using development funds in Africa, rather than a purely military one.

Wheelbarger said she was “heartened” by the initial discussions around PESCO, in particular a focus on lowering legal boundaries that could slow the movement of military equipment between European nations in case of need. That issue has been a major focus for NATO in the years since Russia’s invasion of Ukraine.

But even on an issue of concern for both NATO and PESCO, the U.S. is worried about creating two sets of rules that could complicate the issue.

“Military mobility implemented right would work for both Europe and NATO, but if we don’t have full transparency, if we don’t make sure the requirements for infrastructure or legal changes in between countries isn’t based on NATO requirements, then we’re working at cross purposes,” she warned.

“We just want to make sure there has to be full transparency, so it’s implemented right, so that future initiatives will be based on a positive example,” Wheelbarger added.