The United States and its allies have mapped out detailed plans for coordinated, severe sanctions if Russian troops physically invade Ukraine, but how they should respond to other kinds of aggression is far from agreed upon, U.S. and European officials say.

That ambiguity could slow the pushback Russian President Vladimir Putin will face if Russia repeats past tactics like identifiable cyberattacks, a disinformation campaign, or stepped-up support for pro-Russian separatists.

Senior European diplomats, requesting anonymity, said there had been some planning for "a range of scenarios" and various contingencies, including the kind of cyberattack seen in Ukraine this week that has yet to be conclusively linked to Russia, but any coordinated response would require additional consultations.