(Adds White House comments, paragraphs 8-13)
WASHINGTON, March 11 (Reuters) - Russian responses to U.S. proposals to end the Ukraine crisis do not create the environment for a diplomatic resolution, the United States said on Tuesday, a day before President Barack Obama is scheduled to meet with the Ukrainian prime minister.
Russia's bloodless seizure of Ukraine's Crimea region has brought U.S.-Russian relations to one of their lowest points since the Cold War, with the United States searching for a way to keep Russia from annexing Crimea and its Russian naval base.
U.S. Secretary of State John Kerry spoke to Russian Foreign Minister Sergei Lavrov on Tuesday morning to discuss a series of questions Washington put to Moscow over the weekend in an effort to find a diplomatic solution, the State Department said.
"He (Kerry) also reiterated his willingness to continue to engage with Foreign Minister Lavrov, including this week, but that the environment has to be right and the goal must be to protect the immunity and sovereignty of Ukraine and we didn't see that, obviously, in the responses that we received back," State Department spokeswoman Jen Psaki told reporters.
Psaki said Russia gave its response to the questions on Monday, when the State Department held out the possibility that Kerry might travel to Russia this week but said it needed to know whether Moscow would engage in a diplomatic solution.
While Psaki said Kerry was still open to going to Russia before Sunday's planned referendum in Crimea on whether to join Russia, a poll the United States sees as illegitimate, her comments suggested such a trip was now unlikely.
Kerry told Lavrov "any further escalatory steps will make the window for diplomacy more difficult," Psaki said, adding that he also said "it is unacceptable that Russian forces and irregulars continue to take matters into their own hands."
Obama is set to meet Arseny Yatseniuk, Ukraine's prime minister, on Wednesday at the White House.
Asked what message Russian President Vladimir Putin should take from the meeting, White House spokesman Jay Carney said, "That we strongly support Ukraine, the Ukrainian people and the legitimacy of the new Ukrainian government."
Carney underscored that the United States is seeking a peaceful resolution and Russia still has "an opportunity here to prevent this situation becoming more acute and to prevent the cost to Russia from becoming even higher."
"It is certainly not in Russia's long-term interests to have a destabilized Ukraine. It is not in Russia's interest to find itself isolated from international opinion on these matters," Carney said.
"And it's certainly not in Russia's interest economically to see investors around the world think twice about whether or not Russia is the proper environment for further investment," Carney added.
The United States on Tuesday began military exercises with Polish forces in Poland in the form of air drills using F-16 fighter jets and other aircraft. Bad weather delayed joint U.S. naval exercises in the Black Sea with Romania and Bulgaria. (Reporting by Arshad Mohammed and Will Dunham; Editing by Meredith Mazzilli and Tom Brown)