The Kremlin said Tuesday that there had been a “mix-up” over its reply to the United States on the Ukraine crisis, as diplomatic efforts to deter a Russian invasion picked up pace. State Department officials confirmed Monday they had “received a written followup from Russia” to a document of proposals the US sent to the Kremlin last week on how to defuse tensions and pave the way for further security talks in response to Russia’s demands on security . On Tuesday, however, the Kremlin said that Russia had not yet sent its “main reply” to the US. “There was a mix-up,” Kremlin spokesperson Dmitry Peskov said in 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.” The world might yet get a rare glimpse of Vladimir Putin’s thinking on the tensions later on Tuesday. The Russian President is expected to make an appearance in front of the press in Moscow after meeting the Hungarian Prime Minister Viktor Orban. Diplomats from the US, Russia, Ukraine, NATO and the European Union have been engaged in a flurry of diplomatic activity in recent weeks. On Tuesday, there is also a planned phone call between US Secretary of State Antony Blinken and Russian Foreign Minister Sergey Lavrov, while UK Prime Minister Boris Johnson will meet Ukraine’s President Volodymyr Zelensky. Putin himself has so far remained tight-lipped, making scant public remarks about the crisis, but the news conference following the meeting with Orban may offer some insight. Hungary is a member of both NATO and the European Union, but Orban has cultivated a close relationship with the Russian President. In the past, the Hungarian government has sometimes sided with Russia over Ukraine. In 2019, Budapest vetoed a joint declaration of NATO ambassadors on Ukraine, effectively blocking Ukraine’s attempts at a closer cooperation with the alliance. However, as tension have risen in recent weeks, Hungary, which shares a border with Ukraine, said it was in discussions with the US about the possibility of accepting around 1,000 US and allied troops into Hungary. Meanwhile, Blinken is expected to speak with Lavrov on Tuesday, according to a State Department spokesperson. This call comes on the heels of a heated exchange between the US and Russian ambassadors to the United Nations during a Security Council meeting Monday, with the US saying Russia didn’t give the answers they hoped for and Russia accusing Western UN colleagues of “whipping up tensions and rhetoric.” Build-up of troops continues While the US and its allies continue to pressure Russia to de-escalate the situation, floating the idea of new sanctions and boosting their presence in Eastern Europe, the Pentagon said Russia has continued the buildup of forces around its border with Ukraine. Pentagon spokesperson John Kirby said Monday that additional Russian troops moved “in again around Belarus and around the border with Ukraine” over the weekend, adding that Russia was also increasing its “naval activity in the Mediterranean and the Atlantic.” “They have put to sea more ships, they are exercising at sea, they are clearly increasing the capabilities they have at sea, should they need it,” Kirby said. Both the added ground troops in Belarus and near the Ukrainian border as well as the Russian fleet vessels at sea are creating “options available to Mr. Putin,” Kirby said. Wider diplomatic efforts will also continue on Tuesday with a series of meetings involving Ukraine officials. UK Prime Minister Johnson was traveling to Kyiv Tuesday for talks with President Zelensky. In the runup to the meeting, Johnson announced £88 million ($118 million) in new funding for Ukraine aimed at helping the country achieve “stable governance and energy independence,” according to a statement from Downing Street. Dutch Prime Minister Mark Rutte was also scheduled to visit Ukraine on Tuesday. In a statement posted on his official Twitter account on Monday, Rutte said he spoke with the UN Secretary-General Antonio Guterres and NATO Secretary General Jens Stoltenberg and would speak to the French President Emmanuel Macron before his trip on Tuesday. Macron himself spoke to Zelensky and to Putin on Friday, and then again to the Russian President on Monday. A readout of the call from the Elysee Palace said 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 trying to broker peace in eastern Ukraine since 2014.