The Kremlin admitted Tuesday that there had been a “mix-up” in its response to the US over the Ukraine crisis, as diplomatic efforts to deter a Russian invasion accelerated.

Officials at the State Department confirmed Monday that they had “received a written follow-up from Russia” to a document of proposals sent to the Kremlin last week on how to defuse tensions and pave the way for further security talks in response to Russia’s security demands.

However, the Kremlin stated on Tuesday that Russia had not yet sent its “main response” to the US. “There was a misunderstanding,” Kremlin spokesman Dmitry Peskov said during a conference call. “It [the Russian correspondence] regarded a different matter. The main reply on this issue hasn’t been handed over, it’s still being prepared.”

Later on Tuesday, the world may get a rare glimpse of Vladimir Putin’s thoughts on the tensions. After meeting with Hungarian Prime Minister Viktor Orban, Russian President Vladimir Putin is expected to address the press in Moscow.

Diplomats from the United States, Russia, Ukraine, NATO, and the European Union have been busy in recent weeks. On Tuesday, US Secretary of State Antony Blinken will speak by phone with Russian Foreign Minister Sergey Lavrov, and UK Prime Minister Boris Johnson will meet Ukraine’s President Volodymyr Zelensky.

Putin has remained tight-lipped about the crisis thus far, making few public comments about it, but the news conference following the meeting with Orban may provide some insight. Hungary is a NATO and European Union member, but Orban has developed a close relationship with Russian President Vladimir Putin. In the past, the Hungarian government has occasionally sided with Russia in disputes involving Ukraine. Budapest vetoed a joint declaration of NATO ambassadors on Ukraine in 2019, effectively blocking Ukraine’s efforts to strengthen ties with the alliance.

However, as tensions have risen in recent weeks, Hungary, which shares a border with Ukraine, has stated that it is in talks with the US about accepting up to 1,000 US and allied troops into the country.

Meanwhile, according to a State Department spokesperson, Blinken is scheduled to meet with Lavrov on Tuesday. This call comes after a heated exchange between the US and Russian ambassadors to the UN during a Security Council meeting on Monday, with the US accusing Russia of failing to provide the answers it desired and Russia accusing Western UN colleagues of “whipping up tensions and rhetoric.”

While the United States and its allies continue to put pressure on Russia to de-escalate the situation, threatening new sanctions and increasing their presence in Eastern Europe, the Pentagon reported that Russia has continued to build up forces along its border with Ukraine.

According to Pentagon spokesperson John Kirby, additional Russian troops moved “in again around Belarus and around the border with Ukraine” over the weekend, and Russia was also increasing its “naval activity in the Mediterranean and the Atlantic.”

On Tuesday, broader diplomatic efforts will continue with a series of meetings involving Ukrainian officials.

The UK Prime Minister, Boris Johnson, was in Kyiv on Tuesday for talks with President Zelensky. In the run-up to the meeting, Johnson announced £88 million ($118 million) in new funding for Ukraine, with the goal of assisting the country in achieving “stable governance and energy independence,” according to a Downing Street statement.

On Tuesday, Dutch Prime Minister Mark Rutte was also scheduled to visit Ukraine. Rutte said in a statement posted on his official Twitter account on Monday that he had spoken with UN Secretary-General Antonio Guterres and NATO Secretary-General Jens Stoltenberg, and that he would speak with French President Emmanuel Macron before his trip on Tuesday.

Macron spoke with Zelensky and Putin on Friday, and then again with the Russian President on Monday. According to an Elysee Palace readout, Putin and Macron wished to “continue the dialogue” in the Normandy Format, a four-way conversation between representatives from Ukraine, Russia, Germany, and France that has been attempting to broker peace in eastern Ukraine since 2014.