Washington (CNN) Top Senate Republicans are pledging to find out if the White House is intentionally delaying new sanctions on Moscow as the Trump administration is several weeks past a congressionally-imposed deadline to identify top Russian officials involved in political cybermeddling.

"We're going to check into it," Republican Sen. Bob Corker, the chairman of the Senate Foreign Relations Committee, told CNN Wednesday. "I will find out in the next 24 hours. I'm going to get on the phone with someone and find out."

Sen. John McCain, R-Arizona, who chairs the Senate Armed Services Committee, said the administration is acting "as if they are unilateral."

"We have to do what we need to assert our role," he told CNN.

Corker and McCain are among Trump's fiercest Republican critics in Congress.

The White House is under fire as the deadline to begin the process of slapping fresh sanctions on Russia passed three and a half weeks ago. Administration officials said Wednesday a review process was still underway to identify individuals connected to the Russian defense and intelligence services. The White House pinned the missed deadline on the State Department.

Preparing to see Putin

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The delay comes as Trump prepares to see Russian President Vladimir Putin for the second time face-to-face during a summit meeting in Vietnam. The White House has declined to say whether the two men plan to sit for formal talks when they both attend the Asia-Pacific Economic Cooperation meeting in Da Nang, but a person close to the administration said Trump's aides are working to arrange a bilateral meeting between the two leaders, although the details have not been finalized.

Announcing a new round of sanctions against Russia for its cyber intrusions into last year's presidential election ahead of talks with Putin would prove provocative. Putin has denied Russian involvement in election meddling, and Trump -- who did express concerns about the cyber intrusion during his first meeting with Putin in July -- has nevertheless called the intelligence community findings that Moscow worked to sway the election in his favor a "hoax."

It was that attitude which prompted US lawmakers over the summer to approve legislation that required Trump to impose new sanctions on those involved in Russia's cyber efforts. Trump signed the law grudgingly behind closed doors facing with veto-proof majorities in the House and Senate. But in a signing statement, he expressed constitutional objections to Congress' attempt to sway his foreign policy. And the White House expressed reservations at the law's potential to sour his efforts to improve relations with Russia.

Since then, the administration has taken some steps to comply with the law, including updating an existing set of Treasury sanctions on Russia related to its incursion into Ukraine. On September 29, the White House delegated authorities for identifying those involved in the cyber intrusions to Secretary of State Rex Tillerson and Treasury Secretary Steve Mnuchin.

But the administration did not, as required by the law by the start of October, "issue regulations or other guidance to specify the persons that are part of, or operate for or on behalf of, the defense and intelligence sectors of the Government of the Russian Federation."

Neither the State Department nor the White House could say when the assessment -- which was required by law to be completed by October 1 -- would be finished, saying only that it would be announced "soon."

White House 'remains committed'

White House press secretary Sarah Sanders insisted the administration "remains committed to holding Russia accountable -- and has on a variety of fronts," citing actions to confront Russia's actions in Syria and recent comments from US Ambassador to the United Nations Nikki Haley condemning Moscow's support for Syrian dictator Bashar al-Assad.

Privately, however, White House officials blamed the State Department for the delay, expressing frustration at the process, which led to the missed deadline.

"There is no deliberate holdup," one official said, adding the memo on beginning implementation of the sanctions should have been prepared and circulated by now.

On Tuesday, the State Department spokeswoman Heather Nauert said the agency was "working to try to complete that process."

"My understanding -- and I'm not working on this myself -- but from our people who are working on it, they tell me that it's pretty complicated, that it can take some time," Nauert said.

The delay had drawn concerns from Republicans and Democrats alike, who worry the administration is slow-walking a process that Trump had already expressed misgivings about when it was being debated over the summer.

'Obey the law'

"They can say whatever they want to. But they have to obey the law. The law is what the Constitution says we have to obey," McCain said, suggesting his armed services panel had the power to enact its own punishment of Russia's cyber behavior.

His Democratic colleague, Sen. Ben Cardin, said he had yet to receive a formal response to a letter he and McCain wrote to the administration late last month pressing for a comprehensive plan for implementing the sanctions required by the law. Cardin said an early October meeting with Tillerson to discuss the matter yielded few answers, and he hadn't heard from the State Department since then.

"I am concerned," Cardin said.

"First of all, the relationship between the different agencies and the White House is unclear. We've seen supposed decisions made and not be carried out," he said. "They've already missed deadlines. We will look at other options."

A person familiar with Cardin's October 11 meeting with Tillerson said the top diplomat assured him the State Department was working on the guidance, and that the administration had no intention of shirking its responsibilities under the law to conduct the review.