OK, you will guess. It's Russia. The Washington Times reports:

A bomb blast near the U.S. Embassy in Tblisi, Georgia, in September was traced to a plot run by a Russian military intelligence officer, according to an investigation by the Georgian Interior Ministry.

Shota Utiashvili, the most senior official in charge of intelligence analysis for the ministry, said in an interview with The Washington Times that the recent spate of bombings and attempted bombings - including what he said was a blast targeting the U.S. Embassy - was the work of Russian GRU officer Maj. Yevgeny Borisov.

But the Georgian Interior Ministry had already named Maj. Borisov as a suspect in December. And they claimed that the EU had evidence supporting that allegation, which the EU then distanced itself from. (That evidence, based on a phone call from Russian forces in Abkhazia to the EU Monitoring Mission, is also presented as the smoking gun in the Washington Times story.)

Those allegations gained little traction, however, so here the story is again. It recalls, ironically, the Russian media's periodic and unsubstantiated reports that the U.S. is rearming Georgia.

The timing of the story is unfortunate (from the Georgian perspective), given the controversy over the photographer/spy scandal, which has heightened the sense that Georgia is exaggerating Russia as an all-purpose "bogeyman," as my colleague Molly Corso put it this week. (The Washington Times report says that its interview with Utiashvili took place "last month," which could explain the clumsy timing.) Anyway, this story won't do anything to change the impression that Georgia is like the little boy who cried wolf, with its constant drumbeat of allegations against Russia.

A bigger question should be, why would Russia do this? What do they have to gain from setting off a bomb at the U.S. Embassy in Tbilisi? Reasonable people can doubt Russia's intentions toward the U.S. and Georgia, but this sort of terror action would be extraordinarily self-defeating.

The only new element to the Washington Times story is an attempt to tie the bombing to the U.S.-Russia reset:

If the Georgian charges are true, it implicates a branch of the Russian military in plotting a lethal attack on U.S. territory three months before the U.S. Senate voted to ratify a new strategic arms control treaty with Moscow touted as the centerpiece of President Obama’s policy to “reset” relations with Moscow...

“These are extraordinarily specific and detailed allegations delivered by the government of Georgia,” said Sen. Mark Kirk, Illinois Republican. “On the basis of this report, the Congress should examine these allegations of a Russian-sponsored attack on a U.S. Embassy and its personnel.

“If true, a Russian-sponsored attack on a U.S. Embassy would constitute the most serious crisis in U.S.-Russian relations since the Cold War and put to lie any ‘reset’ in bilateral relations.”

But the more Georgia cries wolf, the more sober-minded people in Washington are going to be thankful for the reset, and to question how reliable a partner Georgia might be.

UPDATE: Other good takes on this story from Joshua Foust, Daniel Larison and Robert Farley.