US House Speaker Nancy Pelosi threatened US Secretary of State Antony Blinken that if his department does not designate Russia as a "state sponsor of terrorism", Congress would go ahead and make that designation itself, Politico reported on Thursday, citing two sources familiar with the matter.

Pelosi's warned her fellow Democrat during a phone conversation earlier in the week, the source said.

The Secretary of State is the only US authority with a mandate to designate states as sponsors of terror. However, some members of Congress believe there are no legal barriers to the body passing a relevant law and designating Russia without authorization from the State Department, Politico said.

"Congress passing legislation is obviously a more complicated route than the secretary making the designation, but it would give the administration the political cover it needs to escalate economic pressure and rhetoric against [Russian President Vladimir] Putin," the outlet quoted a Democratic as saying.

Both the State Department and Pelosi’s office declined to comment, the news outlet said.

Ukrainian President Volodymyr Zelensky called on the US to designate Russia as a "state sponsor of terrorism" in mid-April, appealing to US President Joe Biden to make the designation. The Ukrainian parliament reiterated the call in early May.

The United States did not sanction the Soviet Union under such designation despite Moscow’s support in the 1970s and 1980s for groups that could be considered "terrorist actors", The Washington Post said at the time.

Several US senators proceeded to promptly draft a relevant resolution, but the State Department proved to be reluctant in proceeding with the designation.

State Department spokesperson Ned Price said in mid-April that officials at his department were looking into the possibility of placing Russia on the list.

"We're taking a close look at the facts. We're taking a close look at the law. Whether it is this authority, whether it's any other authority available to us under the law, we will apply it if it's effective and appropriate," he said. There has been no decision on the matter thus far.

The US views "state sponsors of terrorism" as countries that have systemically supported or dealt with acts of international terrorism on their own or on behalf of government agencies.

As of 2022, the US list includes Cuba, Iran, the Democratic People's Republic of Korea, and Syria.

Amid reports on the matter, Kremlin spokesperson Dmitry Peskov said earlier today that if Washington was to designate Russia a state sponsor of terrorism, bilateral relations between the two countries would be severely affected.

"We assess the consequences of such a step very negatively," Peskov told reporters when asked how Kremlin would react if US congress labels Russia a state sponsor of terrorism.