In a sign of the mounting anxiety, Defense Secretary Lloyd J. Austin III ordered a “temporary” repositioning of 160 National Guard trainers from Ukraine to “elsewhere in Europe,” the Pentagon said on Saturday. The trainers have been working alongside an undisclosed number of Army Green Berets, who will remain in Ukraine for now, officials said.

Despite the warnings, American officials believe that Mr. Putin may not yet have made a final decision to invade, and the West’s diplomatic scramble continued on Saturday. President Emmanuel Macron of France spent one hour and 40 minutes on the phone with Mr. Putin, Mr. Macron’s office said.

Secretary of State Antony J. Blinken and Mr. Austin made separate calls to their Russian counterparts on Saturday. And President Volodymyr Zelensky of Ukraine continued to play down the threat, expressing frustration with Washington.

“The best friend for enemies is panic in our country,” Mr. Zelensky told reporters, in English, while observing a police training exercise in southern Ukraine. “And all this information — that helps only for panic, doesn’t help us.”

Mr. Putin is likely to offer more public clues to his position in the coming days. Mr. Ushakov said Russia’s response to last month’s American security proposals would be made public soon. On Tuesday, Chancellor Olaf Scholz of Germany will travel to Moscow, after holding talks in Kyiv, Ukraine’s capital, the previous day. And on Wednesday — the day that American officials have said a Russian invasion could begin — Mr. Putin is scheduled to host President Jair Bolsonaro of Brazil in Moscow.

The diplomatic flurry came as Russia’s military posture continued to grow more ominous. More than 30 Russian Navy ships — including frigates, missile boats and submarine chasers — set sail for exercises in the Black Sea, Russia’s Defense Ministry said. The deployment strengthened the effective encirclement of Ukraine by Russian forces from all sides but the west.

Ukrainian military officials have grown increasingly concerned about the deployment of special forces and airborne troops to regions near the Ukrainian border. Two days ago, the Kremlin deployed more than 50 attack and transport helicopters to Machulishchi in Belarus and Valuiki in Russia, both within easy striking distance of Ukraine, a senior Ukrainian military official said Saturday. Such helicopters would be used to provide close air support for any ground forces used in an invasion.