Ukraine war: President Biden's words of resolve echo in Europe but worrying developments loom

Joe Biden flies home confident that a well choreographed trip has combined words, pictures and diplomacy to project a message of strength, resolve and unity.

Apart from a stumble as he climbed the steps to Air Force One, he has not put a foot wrong on the four-day whirlwind tour of Poland and Ukraine.

The president ended his visit with a high level NATO meeting he hopes puts diplomatic weight behind the fine oratory and imagery of the week.

Allies on NATO's east flank want reassurance America has their back. They concluded their meeting vowing to fight Russian aggression as one.

In a passionate speech in Warsaw Castle, President Biden had told Poles that Ukraine stood firm and stood proud and America would support it till the end.

But there are worrying developments. In the same week there have been warnings of Russian attempts to destabilise other countries and widen this war, not least in Moldova, which neighbours Ukraine.

And there are concerns China may be drawn in. The US says Beijing is considering sending arms to Russia.

This week Russia's President Vladimir Putin also suspended his country from the START nuclear arms treaty, casting doubt on the entire nuclear weapons control system. The move is being seen in western capitals as more nuclear bullying by the Russian president as the war enters another year.

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President Putin has given no indication he is backing off his Ukrainian misadventure. In a perverted version of recent history he claimed NATO had started this war in a lacklustre speech in the Kremlin delivered on the same day as President Biden's.

It seemed to be preparing Russians for a war without end.

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And there are fears President Putin plans an anniversary surprise to mark the year since he invaded Ukraine in an unprovoked attack 12 months ago this Friday.

If Russia is planning a protracted conflict, the US president and his allies must be ready to maintain their solidarity. Apart from the absence of Kremlin sympathiser Hungarian Prime Minister Viktor Orban at their meeting, there was no sign of disunity. He sent his president instead.

The week started with the president's stunning surprise visit to Kyiv which sent a clear message to allies about his commitment to Ukraine, but he said the trip was about more than that. It was about freedom and democracy everywhere he said, and that is what is at stake in this conflict.

President Biden, the Cold War warrior, has fought for freedom and democracy all his life and now that fight has taken him into a warzone - the first modern president to venture into one not controlled by the US military.

He returns with a sense of mission accomplished while the region braces itself for possible escalation in Ukraine's war soon and a potential widening of the conflict.