On Sunday, Chancellor Angela Merkel told Russian President Vladimir Putin that she regretted a lack of progress on forming an international contact group to solve Ukraine's stalemate, the German government announced. Both houses of Russia's parliament have announced that they would welcome Crimea into the federation.

"The chancellor asserted the German position forcefully that the so-called March 16 referendum on Crimea is illegal," said Merkel's spokesman, Steffen Seibert.

In calls with Merkel and UK Prime Minister David Cameron Sunday, Putin defended the situation in Crimea, where Russia reinforced its presence this weekend. Putin maintains that he answered the call of supporters who feared for their safety following the downfall of Ukrainian President Viktor Yanukovych.

"The steps taken by the legitimate leadership of Crimea are based on the norms of international law and aim to ensure the legal interests of the population of the peninsula," Putin said Sunday, according to the Kremlin.

'A big miscalculation'

On Sunday, UK government officials said that Putin and Foreign Minister Sergey Lavrov would discuss the formation of the contact group to establish direct talks with Ukraine.

"President Putin agreed that it is in all our interests to have a stable Ukraine," a UK government spokeswoman said.

UK Foreign Secretary William Hague stepped up pressure for a solution, saying that the Russian occupation of Crimea could prove a "big miscalculation" in the long term.

"It would be wrong to conclude that Russia has won in some sense," Hague told the BBC Sunday.

Ukrainian Prime Minister Arseniy Yatsenyuk will speak with US President Barack Obama in Washington Wednesday. US officials say the country will not honor any annexation of Crimea.

"We won't recognize it, nor will most of the world," deputy US national security adviser Tony Blinken said.

Schulz speaks

Speaking to a German newspaper, European Parliament President Martin Schulz called for forcing Russia to negotiate with Ukraine's interim government. Schulz, a German Social Democrat, urged officials to guarantee the continuance of Russian operations at the Crimea naval base, where it had stationed its Black Sea Fleet since long before before the stalemate erupted. However, Schulz said Russian President Vladimir Putin would have to comply with international demands to negotiate directly with Kyiv or face tougher sanctions.

"If Russia doesn't find its way to the negotiating table with Ukraine, the EU will step up sanctions," the EU parliament president told the German newspaper Bild am Sonntag. "What's happening in Crimea is a violation of human rights," he added.

German magazine Der Spiegel reported that NATO estimates that 2,000 Russian soldiers occupy Crimea. Some NATO sources believed the number three times as high.

mkg/rc (Reuters, AFP, dpa, AP)