The United States has expressed concern over recent moves in the Ukrainian parliament to remove lawmakers.
The State Department highlighted the case of Serhiy Vlasenko, a lawmaker and defense counsel for former Prime Minister Yulia Tymoshenko.
The State Department said efforts to deprive Vlasenko of his seat in parliament "appear to be politically motivated due to his connection with Tymoshenko."
The State Department also noted the cases of independent lawmakers Pavlo Blaloha and Oleksandr Dombrovsky.
A Ukrainian court last month annulled their parliamentary mandates.
The United States urged the Ukrainian government "to honor the will of Ukrainian voters as expressed in the October 2012 parliamentary elections" and end "politically motivated prosecutions of opposition leaders and to abide by their international commitments to the rule of law and democracy."