Diplomatic efforts to head off what US officials have warned could be an imminent Russian attack on Ukraine are going into a new round on Monday as Germany's chancellor heads for Kyiv.

Over the weekend, some airlines cancelled flights to the Ukrainian capital and troops there unloaded new shipments of weapons from North Atlantic Treaty Organisation (Nato) members on Sunday, as its president sought to project confidence in the face of US warnings of possible invasion within days.

As political leaders look for a way to defuse spiralling tensions, Ukraine's ambassador to Britain has clarified comments appearing to suggest that his country could consider dropping its ambition to join Nato to avoid war with Russia.

Here's a look at what is happening where and why.

What is the German leader bringing?

German Chancellor Olaf Scholz's first visit to Kyiv since taking office in December comes before his first visit to Moscow on Tuesday. It's part of a flurry of in-person and remote diplomacy by Western leaders.

Scholz is taking a message of solidarity to Ukrainian President Volodymyr Zelenskyy after criticism of Germany for its refusal to join some allies in sending lethal weapons to the country.

Scholz said on Sunday that Ukraine "could be sure that we will show the necessary solidarity, as we did in the past", pointing to financial aid to Kyiv in the past.

He renewed his warning that Russian military aggression against Ukraine “will lead to tough responses and sanctions that we have carefully prepared and that we can make effective immediately, together with our allies in Europe and in Nato".

Scholz will meet Russian President Vladimir Putin on Tuesday.

What's with Ukraine's Nato ambitions?

Ukraine's ambassador to Britain has clarified comments appearing to suggest that his country could consider dropping its ambition to join Nato to avoid war with Russia.

Vadym Prystaiko told BBC radio on Sunday that "we might drop the ambition, which is enshrined in Ukraine's constitution, because Ukraine is being blackmailed."

Read: Echoes of the Cold War

"What I'm saying here is that we are flexible, trying to find the best way out," the ambassador said. "If we have to go through some serious concessions, that's something we might do."

On Monday, Prystaiko said there had been a misunderstanding. He said that to avoid war we are ready for many concessions.

But it has nothing to do with Nato, which is enshrined in the constitution, he said.

How is Ukraine's president faring?

Zelenskyy was elected as president in a landslide victory in 2019. As a political novice making an unlikely bid for the job, he had vowed to reach out to Russia-backed rebels in the east who were fighting Ukrainian forces and make strides toward resolving the conflict.

But Zelenskyy is watching his once-enormous support dissolve as Ukraine faces fears of a Russian invasion that could not only take the rebel regions but possibly the rest of the country.

To make matters worse, the incumbent whom Zelenskyy defeated in 2019 has boldly returned to the country to face charges of treason and stir up opposition to him.

Analysts suggest that Moscow is seeking to bolster support among pro-Russia politicians in Ukraine and that the buildup of Russian forces near Ukraine's border is aimed partly at destabilising the country's politics.