The possibility of a diplomatic resolution to the crisis in Ukraine dimmed Friday as Crimean authorities prepared for a referendum on whether to split from Ukraine and join Russia, which made clear it would welcome the region like a long-lost brother.

A day after President Obama denounced the referendum and ordered sanctions over Russia’s intervention in the autonomous region, Russian President Vladi­mir Putin rejected the U.S. position, saying he could not ignore what he described as “calls for help” from ethnic Russians in Ukraine.

In Moscow, Russian lawmakers warmly applauded a Crimean delegation, calling the referendum legitimate and pledging their support if Crimea comes back to Russia.

Ukraine’s prime minister, Arseniy Yatsenyuk, said the world would not recognize the “so-called referendum” set for March 16 if Crimean voters elected to go with Russia. He said that Kiev would hold direct talks with Moscow but that Russia must first pull back its troops now believed to be scattered at checkpoints and military bases across Crimea and halt its support for “separatists and terrorists.”

With just more than a week before the vote, the heated rhetoric underscored how likely it appeared that Crimeans will opt for Russia. The regional parliament voted Thursday to join Russia and called the referendum to ratify its decision. Almost six in 10 people in Crimea are ethnic Russians and Russian speakers.

Crimean officials are printing 2.2 million ballots, in Russian, Ukranian and Crimean Tatar, asking voters to choose whether to stick with Ukraine or be annexed to Russia.

Secretary of State John F. Kerry and his Russian counterpart, Sergei Lavrov, spoke on the telephone Friday, after meeting twice in person this week. U.S. sanctions against Russia will “inevitably boomerang,” Lavrov told Kerry, according to a Russian Foreign Ministry statement reported by the Interfax news agency.

“Lavrov cautioned against hasty and ill-considered moves that can damage Russian-American relations, especially sanctions,” the statement said. The ministry said the two diplomats were planning further meetings.

Defense Secretary Chuck Hagel telephoned Ukraine’s defense minister Friday to stress “the firm commitment of the United States” to support Ukraine, and to praise “the performance and the restraint [of] the Ukrainian armed forces, who have not allowed this situation to escalate,” Pentagon spokesman Rear Adm. John F. Kirby said.

Kirby confirmed that aircraft would be sent to Poland to “plus-up” an existing U.S. aviation attachment based in Poland, but said decisions on numbers and timing have not been made. The Defense Department sent six F-15 fighter jets to Lithuania this week after Baltic nations requested additional defense assets as part of an existing air patrol mission.

Kirby also clarified that the USS Truxtun, a guided-missile destroyer, was in the Black Sea as part of a routine deployment scheduled before the upheaval in Ukraine.

Asked about the number of Russian troops in Crimea, he put the total at “near 20,000,” including up to 6,000 that have been newly deployed, in addition to those already stationed at Russian bases in the Ukrainian region. Russia has denied sending any additional troops to Crimea.

See the Ukrainian crisis in detailed maps

Also on Friday, Obama spoke with German Chancellor Angela Merkel, and they “agreed on the need for Russia to pull back its forces, allow for the deployment of international observers and human rights monitors to Crimea, and support free and fair presidential elections in May,” the White House said in a statement.

Warning from Gazprom

Russia’s presence in Crimea appears to be increasing by the day. Entrances to ports and military bases are guarded by Russians in uniforms without insignia or local militias wearing ribbons that identify them as pro-Russian. Moscow has denied that its troops are spread around the region, outside of its Black Sea Fleet quarters.

Meanwhile, Gazprom, the Russian state gas monopoly, warned that gas supplies might dry up unless Kiev settled its debts.
Alexei Miller, the head of Gazprom, said Ukraine’s debt to the Russian monopoly had jumped to $1.89 billion after Kiev missed Friday’s deadline to settle the bill for last month’s deliveries. “We can’t supply gas for free,” he said.

International efforts to defuse the crisis have been stymied. On Friday, for the second time in two days, 47 military and civilian observers from the Organization for Security and Cooperation in Europe were blocked from entering Crimea, according to Agence France-Presse. The team was stopped by armed men at a checkpoint flying a Russian flag.

Pro-Russia sentiment is strongest in Sevastopol, a picturesque city of about 400,000 people that is home to Russia’s Black Sea Fleet. Few people speak Ukrainian, and many residents say they think of themselves first as Russian.

Local television stations have been broadcasting lengthy videos of the protests in Kiev that led to the ouster last month of the Ukrainian president, Viktor Yanukovych. The videos, played with menacing music in the background, show random acts of violence including protesters throwing molotov cocktails. They are followed by a montage of Russian soldiers from World War II and modern-day Russian sailors firing guns from ships to protect Crimea, all set to music that sounds uplifting and glorious.

Many residents of Sevastopol say they consider the upcoming referendum an inevitability decades in the making.

“People have been waiting for this for 23 years,” said Olga Manko, an official with the Russian Bloc, the largest pro-Russia party in Crimea, who was referring to the 1991 collapse of the Soviet Union.

Gallina Glebova, a restaurant manager, said she doesn’t know anyone who wants to stay with Ukraine. “We are inseparable from Russia,” she said. “We don’t have to think how we want to vote. It will be unanimous.”

There are people in Crimea who oppose breaking off from Ukraine, and many say they fear they will be harassed and expelled if the measure passes.

“People will be given Russian passports, and those who didn’t vote in favor of joining Russia could be deported,” said Viktor Neganov, a Sevastopol activist who opposes separation and was beaten by pro-Russia demonstrators. “We won’t have any other option. We will have to leave Crimea.”

Moscow demonstration

In Moscow, tens of thousands of people joined a rally and concert in Red Square on Friday to support Crimea’s aspirations to secede and join Russia.

Participants carrying banners saying “We Believe in Putin,” “Save Crimea From Fascists” and “Crimea Is Russian Land” flocked to the square at the end of the working day and gathered around a stage near the Kremlin to listen to patriotic speeches and songs.

Organizers distributed orange and black ribbons — the colors of Saint George that commemorate the Soviet victory over Nazi Germany in World War II.

One man, who would not give his name for fear of reprisals, said his employers had ordered him to attend the rally. “I love my motherland and I am for Crimea, so it’s all right to be here,” he said, adding that he would have been fired had he refused to attend. “You should understand that not much has changed since the Soviet Union. We don’t have gulags anymore of course, but punishments are still very tough.”

On the streets of Kiev on Friday, many expressed a sense of frustrated helplessness. “No, I’m not happy about it. Crimea is part of Ukraine,” said Tanya Pyantkovska, 18, a university student who was visiting memorials in Independence Square to those killed in the protests. “But what can we do?”

Lally reported from Moscow. Isabel Gorst in Moscow, Karen DeYoung in Washington and Anthony Faiola in Kiev contributed to this report.