In a cautious report that did not identify the source of the intelligence or the group involved, The New York Times said US officials had no evidence implicating Ukrainian President Volodymyr Zelenskyy in the pipeline bombing.
But the attack benefited Ukraine by severely damaging Russia's means of reaping millions by selling natural gas to Western Europe.
At the same time, it added to the pressure of high energy prices on key Ukrainian allies in Europe, particularly Germany.
Ukraine has denied any involvement in the operation.
Ukrainian presidential adviser Mykhailo Podolyak also tweeted that "Ukraine has nothing to do with the Baltic Sea mishap and has no information about pro-Ukraine sabotage groups".
The intelligence suggested the perpetrators behind the sabotage were “opponents of President Vladimir V Putin of Russia”, the Times report said.
US officials had no indication of who exactly took part and who organised and paid for the operation, which would have required skilled divers and explosives experts.
They believed those involved were probably Ukrainian or Russian citizens, and that none were from the US or Britain.
Investigators in Germany believe the unidentified group was made up of five men and one woman using professionally falsified passports, according to a separate report from several German media outlets.
German officials had identified the boat suspected to have been used in the attack, according to the broadcasters ARD, SWR and weekly Zeit.
The commando group is said to have set sail from the north German port of Rostock on September 6 last year and landed the following day on the Danish island of Christianso in the Baltic.
The yacht was subsequently returned to the owner uncleaned, with investigators able to find traces of explosives on the table in the cabin, the detailed report showed.
The pipelines were ruptured by subsea explosives on September 26, seven months after Russian forces invaded Ukraine.
US officials have “no firm conclusions” about the intelligence, “leaving open the possibility that the operation might have been conducted off the books by a proxy force with connections to the Ukrainian government or its security services”, the Times said.
The lack of a firm suspect meant international intelligence officials had not ruled out the possibility of a “false flag” operation to link the attack to Ukraine, per the German media.
Authorities in Germany, Sweden and Denmark have opened investigations into the incident.
A spokeswoman for the German government said it had “taken note” of the Times report, referring back to the ongoing investigation.
“There is an ongoing preliminary investigation in Sweden, so I do not intend to comment on those reports,” Swedish Prime Minister Ulf Kristersson told reporters late on Tuesday.
Speaking at the same press conference, Nato Secretary General Jens Stoltenberg echoed those remarks, saying it would be “wrong to speculate” before the investigations were completed.
Agence France-Presse contributed to this report