The two Russian intelligence agents, arrested last month, are in detention charged with killing the former Chechen president Salim Khan Yandarbiyev. He died after his car blew up in the Qatari capital Doha as he was returning home from Friday prayers on 13 February.
"Concerning the arrest of the Russians, we provided minor technical assistance to Qatar but for the most part, the Qataris acted themselves," US deputy assistant secretary for European and Eurasian affairs Steven Pifer told the Vremya Novostei daily on Monday.
The head of parliament's foreign affairs committee, Konstantin Kosachev, rounded on the US on Monday for having helped detain the secret agents in Qatar.
"We can only regret that the United States did not give technical or political assistance to the international community to find Yandarbiyev and put an end to the criminal activities of that international terrorist," ITAR-TASS quoted the senior Russian lawmaker as saying.
Russia has demanded that Qatar free the two Russian agents, denying that they had anything to do with the murder of Yandarbiyev of the breakaway republic of Chechnya.
The affair has turned into a full-blown diplomatic row. Moscow detained two Qatari citizens in transit on 26 February, in apparent retaliation, and is reported to be negotiating a swap.
"...we provided minor technical assistance to Qatar but for the most part, the Qataris acted themselves"
deputy assistant secretary, US
The two men, a Qatari official with the Qatar Greco-Roman wrestling team and an Azeri who has Qatari citizenship and competes for the team, were detained at Moscow's Sheremetyevo airport carrying $7,200, which they had not declared to customs.
The Federal Security Service (formerly the KGB) said on 19 March the two were being held in the high-security Lefortovo prison. The FSB said they would face "lengthy prison terms if convicted" but declined to say on what charges.
Russia had accused Yandarbiyev of helping finance Chechen separatists who have been at war since 1999.
Qatar had declined to extradite Yandarbiyev, who briefly served as Chechen president at the end of the first Chechen war from 1994 to 1996.