A week after Russian troops deployed in Ukraine’s southern Crimea peninsula, Washington on Monday called on Russia to prove that it was willing to act on a series of US proposals aimed at facilitating dialogue between Kiev and Moscow and ending the crisis.

US Secretary of State John Kerry had laid out a number of ideas to his Russian counterpart Sergey Lavrov and is prepared to take part in further talks “if and when we see concrete evidence that Russia is prepared to engage on these proposals,” State Department spokeswoman Jen Psaki said.

The top US diplomat had sent the ideas to Lavrov and discussed them in a phone call on Saturday, but had yet to receive any reply.

In the phone call, Kerry said “the United States wants to see a cessation of Russian military advances in Ukraine including Ukraine’s Crimean Peninsula, a halt in the drive for annexation of Crimea, and the end of provocative steps to provide space for diplomacy,” Psaki said in a statement.

“We are still awaiting a Russian response to the concrete questions that Secretary Kerry sent Foreign Minister Lavrov on Saturday in this regard,” Psaki added.

Russia said Monday it will unveil its own solution to the Ukrainian crisis that runs counter to US efforts and appears to leave room for Crimea to switch over to Kremlin rule.

Lavrov said he had invited Kerry to visit Moscow on Monday and that proposals he had received from Kerry on resolving the stand-off “do not suit us very much.”

Ukraine’s new pro-European leaders are racing against the clock to rally Western support in the face of the seizure by Kremlin-backed forces of the strategic Black Sea peninsula and plans to hold a referendum on Sunday to switch its allegiance from Kiev to Moscow.

US President Barack Obama will welcome Ukraine’s new prime minister Arseniy Yatsenyuk to the White House on Wednesday, in a show of support for the new authorities in Kiev.

“I think it will reinforce the fact that the United States believes that the Ukrainian government has responsibly filled the vacuum left by the sudden, hasty and voluntary departure” of Ukrainian president Viktor Yanukovych, White House spokesman Jay Carney said.

Meanwhile Monday, UN Secretary-General Ban Ki-moon urged all parties in Ukraine “to refrain from hasty actions and provocative rhetoric.”

The UN chief warned that “at this crucial juncture, we cannot afford either miscalculations or inaction,” adding that “a further deterioration of the situation would have serious repercussions for the people of Ukraine, the region and the global community.”

He said a resolution to the crisis must be based on the principles of the UN Charter, including “the peaceful settlement of disputes and respect for the unity, sovereignty and territorial integrity of Ukraine.”

In Moscow, Russia’s Foreign Ministry on Monday denounced what it called lawlessness by far-right activists in eastern Ukraine, a statement likely to trigger alarms in Ukraine about possible Russian intervention there.

Ukraine’s foreign minister said Monday his country already feels like it’s almost in a state of war after Russian forces took effective control of Ukraine’s Crimean Peninsula. A referendum has been called there for Sunday on whether the region should split off and seek to become part of Russia.

Pro-Russia sentiment is also high in Ukraine’s east and there are fears Russia could seek to incorporate that area as well.

In its Monday statement, the Russian foreign ministry said lawlessness “now rules in eastern regions of Ukraine as a result of the actions of fighters of the so-called ‘Right Sector’ with the full connivance” of Ukraine’s new authorities.

Right Sector is a grouping of several far-right and nationalist factions. Its activists were among the most radical and confrontational of the demonstrators in the Ukrainian capital, Kiev, and organized “self-defense” brigades for the protest camp

The Kremlin statement also claimed Russian citizens trying to enter Ukraine have been turned back at the border by Ukrainian officials.

On Monday in Kiev, Ukrainian Foreign Minister Andriy Deshchytsya received his counterparts from Belgium, the Netherlands and Luxembourg, who had come to show support for Ukraine in what has turned into Europe’s greatest geopolitical crisis since the end of the Cold War.

“We have to admit that our life now is almost like… a war,” Deshchytsya said, speaking in English. “We have to cope with an aggression that we do not understand.”

He said Ukraine is counting on help from abroad to deal with its giant neighbor to the east.