Senate Majority Leader Harry ReidHarry ReidChris Murphy’s profile rises with gun tragedies Republicans are headed for a disappointing end to their year in power Obama's HHS secretary could testify in Menendez trial MORE (D-Nev.) said Monday that a “few radical Republicans” blocked progress on a Ukraine aid package more than a week ago because they are trying to protect the Koch brothers.

Reid tried to get an up-or-down vote on the Senate Ukraine bill more than a week ago, but some Republicans objected saying they wanted to add a delay to Internal Revenue Service (IRS) regulations on tax-exempt groups if Democrats were allowed to include reforms to the IMF.

“It’s almost unimaginable why they blocked it,” Reid said ahead of the vote. “A few radical Republicans delayed this aid package by 10 days in order to protect the Koch brothers and billionaires like them.”

Reid has increasingly been critical of oil billionaires David and Charles Koch, who fund conservative political groups such as Americans for Prosperity. Reid has accused them of trying to “buy America” through political donations.

Later Monday, the Senate will take the first procedural vote on whether to proceed to a Ukraine aid bill that includes sanctions against Russians who invaded the Crimea peninsula.

Reid said the delay in Senate action sent a "dangerous" message to Russia. 

“When a few extremist Republicans blocked action on this robust bill reported with strong, bipartisan support by the Foreign Relations Committee, it sent a dangerous message to Russian leaders,” Reid said. 

The Senate bill, S. 2124, from Senate Foreign Relations Committee Chairman Bob Menendez (D-N.J.) has bipartisan support in the Senate, but the House will be voting on a different measure later this week that doesn’t include the changes to the IMF.