The Trump administration on Wednesday briefly sparked confusion when it issued updated policy guidance saying some children of U.S. government employees and service members who live abroad may not be considered to be residing in the U.S. for the purposes of automatically acquiring citizenship.

The guidance by U.S. Citizenship and Immigration Services (USCIS) replaced previous input saying any child born of a U.S. government official or service member abroad would automatically acquire citizenship.

The new guidance applies only to a small group of children born abroad and does not affect children who are citizens at birth or who have already acquired citizenship.

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USCIS identified three sets of children living outside the U.S. whom the policy could affect: children of non-U.S. citizens adopted by U.S. citizen employees or service members; children of non-U.S. citizen parents who become citizens after the child’s birth; and children of U.S. citizens who do not meet residency requirements to transmit citizenship to their children at birth.

“For them to obtain a Certificate of Citizenship, their U.S. citizen parent must apply for citizenship on their behalf under [Immigration and Nationality Act] 322, by filing Form N-600K, and show they meet the qualifications under that provision,” a spokesman said.

“Certain children of U.S. service members may complete the process outside of the United States without having to travel to the United States. However, children of U.S. government employees must enter the U.S. lawfully with an immigrant or nonimmigrant visa and be in lawful status when they take the oath of allegiance, which completes the process.”

The agency said the reason for the policy update was because it conflicted with the definition of “residence” under a part of the Immigration and Nationality Act (INA) enacted in 2008 after existing guidance was issued. It also had conflicted with State Department guidance, which it said could lead to “inconsistent” decisions on citizenship claims, according to the agency.

The Trump administration has been eyeing the thorny question of automatic birthright citizenship for some time -- particularly the policy under which the children of illegal immigrants are granted birthright citizenship. The USCIS guidance did not affect that question, but it initially sparked confusion among journalists -- some of whom deleted tweets after accidentally misconstruing the policy -- and anger among some military groups.

House Speaker Nancy Pelosi, D-Calif., blasted the change, calling it an "attack" on military families and diplomats abroad and saying "shameful policy must be reversed immediately."

"America’s servicemembers & diplomats abroad are among our nation’s best, yet @realDonaldTrump is launching an attack on their families, putting in doubt the citizenship of their children born overseas. This shameful policy must be reversed immediately, she tweeted.

“Military members already have enough to deal with, and the last thing that they should have to do when stationed overseas is go through hoops to ensure their children are U.S. citizens,” Andy Blevins, the executive director of Modern Military Association of America -- a nonprofit for LGBTQ military and veteran families -- said in a statement.

However, Acting USCIS Director Ken Cuccinelli tweeted that members of the media were going “crazy” and that “the highly technical policy manual used by career employees here as a reference was updated today to conform USCIS practices with the Department of State -- that's it. But some people are freaking out over nothing."

He later said in a statement that the policy “does not affect who is born a U.S. citizen, period.”

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“This only affects children who were born outside the United States and were not U.S. citizens,” he said in the statement. “This does NOT impact birthright citizenship. This policy update does not deny citizenship to the children of U.S. government employees or members of the military born abroad.”

“This policy aligns USCIS’ process with the Department of State’s procedure, that’s it,” he said.

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A Pentagon spokeswoman said the Defense Department “understands the estimated impact of this particular impact is small.

“However, we are committed to ensuring affected families are provided the appropriate information, resources and support during this transition,” Lt. Col. Carla Gleason said.

Fox News’ Rich Edson, Kellianne Jones, John Roberts and Lucas Tomlinson contributed to this report.