Former Secretary of State Rex Tillerson Rex Wayne TillersonGary Cohn: 'I haven't made up my mind' on vote for president in November Kushner says 'Alice in Wonderland' describes Trump presidency: Woodward book Conspicuous by their absence from the Republican Convention MORE ordered State Department officials to make the case for declaring Russia a state sponsor of terrorism earlier this year, before abruptly ending the initiative.

Pro Publica reported Monday that the initial order from Tillerson came after a former Russian spy and his daughter were poisoned with a military-grade nerve agent on British soil. Western officials have blamed Moscow for the poisoning.

The decision to back away from the plan days later is reflective of how the U.S. has continued to seek Moscow's cooperation on combatting terrorism, particularly in the Middle East.

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“There are a lot of issues that we have to work on together with Russia,” a U.S. official told Pro Publica. “Designating them would interfere with our ability to do that.”

Still, the U.S. has become increasingly concerned about what officials have said are brazen aggressions and destabilizing activities by Russia, such as its efforts to meddle in foreign elections and its support for the Syrian and Iranian governments.

The U.S. has long accused Iran of supporting terrorism, because of its backing of groups like Hezbollah in Lebanon, which Washington considers a terrorist organization.

The U.S. joined dozens of countries in March in expelling Russian diplomats in retaliation for the poisoning of Sergei Skripal, a former Russian double agent, and his daughter, Yulia.

Moscow has denied that it was behind the attack, and has blamed Washington for orchestrating a blackmail campaign against Russia.