In August 2018, the State Department determined that the deadly use of the nerve agent, Novichok, had violated a 1991 law passed by Congress to stigmatize the use of chemical and biological weapons. That prompted an initial round of sanctions with little bite, given that they largely mandated penalties that the United States had already applied to Russia for other reasons.

The law, known as the Chemical and Biological Weapons Control and Warfare Elimination Act, also requires the administration to certify that a country found to have employed such weapons has stopped their use, has provided assurances it will not do so again and has allowed for on-site inspections. Because Russia continues to maintain that it was not behind the botched poisoning, the State Department notified Congress in November that it could not make such a determination.

That the Trump administration did not follow through with the additional penalties prescribed by law frustrated lawmakers. In May, the under secretary of state for arms control and international security, Andrea Thompson, told a Senate panel that the State Department had “teed up” the additional sanctions.

“We’ve been extremely vocal and active in pushing back on Russia’s heinous attack on the Skripals,” Ms. Thompson insisted, suggesting that the slow action on sanctions was “part of a larger Russia strategy.”

On Monday, the top Democrat and Republican on the House Foreign Affairs Committee sent a joint letter to the White House threatening new congressional action to force the administration’s hand.

“Failure by the administration to respond to Russia’s unabashed aggression is unacceptable and would necessitate that Congress take corrective action,” wrote the members, Eliot L. Engel, Democrat of New York, and Michael McCaul, Republican of Texas.

The law provided the administration with numerous sanctions to choose from. The executive order released by the White House on Thursday banned loans or other assistance to Russia by international financial institutions and prohibited most loans from American banks to Russia’s government.