Putin declares Crimea 'sovereign and independent'

Moscow, meanwhile, called on Ukraine to become a federal state as a way of resolving the polarization between Ukraine's western regions - which favor closer ties with the 28-nation EU - and its eastern areas, which have long ties to Russia.

In a statement Monday, Russia's Foreign Ministry urged Ukraine's parliament to call a constitutional assembly that could draft a new constitution to make the country federal, handing more power to its regions.

It also said country should adopt a "neutral political and military status," a demand reflecting Moscow's concern about the prospect of Ukraine joining NATO and possibly integrating closer politically and economically with the EU.

Russia is also pushing for Russian to become one of Ukraine's state languages alongside Ukrainian.

In Kiev, Ukraine's new government dismissed Russia's proposal Monday as unacceptable, saying it "looks like an ultimatum."

The new government in Kiev was established after pro-Russian President Viktor Yanukovych fled to Russia last month after three months of protests culminated in deadly clashes.

Ukrainian Foreign Minister Andriy Deshchytsya visited NATO headquarters in Brussels to request technical equipment to deal with the secession of Crimea and the Russian incursion there.

NATO said in a statement that the alliance was determined to boost its cooperation with Ukraine, including "increased ties with Ukraine's political and military leadership."