3 Democratic senators ask about Ukraine involvement in Robert Mueller probe

Washington (CNN)Three Democratic senators have written a letter to Ukraine's prosecutor general to "express great concern" over reports that Ukrainian officials had looked to potentially hinder special counsel Robert Mueller's Russia investigation.

Sens. Bob Menendez of New Jersey, Dick Durbin of Illinois and Patrick Leahy of Vermont wrote in the letter to Yuriy Lutsenko that a recent New York Times report said his office "effectively froze investigations into four open cases in Ukraine in April, thereby eliminating scope for cooperation with the Mueller probe into related issues."
Ukrainian investigators had been tracing money paid to Paul Manafort, who would later become Trump's campaign chairman, by figures in the political party of pro-Russian Ukrainian President Viktor Yanukovych, the Times reported. Yanukovych was ousted from power in 2014. The decision to halt the investigations came at a delicate moment for Ukraine, as the Trump administration was finalizing plans to sell it anti-tank missiles called Javelins, the Times reported.
The May 4 letter requests that Lutsenko answer three questions, which include inquiries about whether the office did attempt to "restrict cooperation" with Mueller's probe and "if so, why?"
    It also asks if anyone from the Trump administration encouraged "Ukrainian government or law enforcement officials not to cooperate" with Mueller's investigation, and if that probe was "raised in any way during discussions between your government and US officials, including around the meeting of Presidents Trump and Poroshenko in New York in 2017," a reference to Ukrainian President Petro Poroshenko.
    Mueller is investigating Russia's attempts to influence the 2016 US presidential election and is looking into any potential ties between Trump campaign associates and Russia's efforts. Trump has repeatedly denied any collusion.
    "As strong advocates for a robust and close relationship with Ukraine, we believe that our cooperation should extend to such legal matters, regardless of politics," the three senators wrote.
    "Blocking cooperation with the Mueller probe potentially cuts off a significant opportunity for Ukrainian law enforcement to conduct a more thorough inquiry into possible crimes committed during the Yanukovich era," they wrote. "This reported refusal to cooperate with the Mueller probe also sends a worrying signal -- to the Ukrainian people as well as the international community -- about your government's commitment more broadly to support justice and the rule of law," the statement continued.