By Richard Roth CNN

NEW YORK (CNN) -- The UK ambassador to the UN said Wednesday his country has evidence that Syria used sarin gas on its own people last week.

Ambassador Matthew Rycroft told the UN Security Council UK chemical weapons scientists have analyzed samples obtained from Khan Shaykhun, the site of the attack on April 4. Rycorft told the council "these have tested positive for the chemical nerve agent sarin or a sarin-like substance. The United Kingdom therefore shares the US assessment that it is highly likely the regime was responsible for a sarin attack on Kham Shaykhun."

It a big day for Syria at the UN. A showdown vote by the Security Council is planned for later Wednesday on a proposed UN resolution that would compel the Syrian regime to provide helicopter pilots and flight logs from the day of the attack to outside investigators. The resolution condemns the attack.

Russian government officials in Moscow have stated they intend to veto the measure. Swedish Ambassador Olof Skoog told reporters a Russian veto would be bad for the Security Council and also for Moscow.

A planned vote on a resolution collapsed Thursday night at the UN as the US launched missiles on a Syrian base believed to be responsible for the chemical attack.

In his speech, Rycroft blasted the Russians for supporting the Assad regime. He said the Syrian people "have suffered six years of ever-escalating barbarity, over six years of failed ceasefires, and over the years, Russia has held us ransom for the Assad regime."

He pointed to Bashar al-Assad directly: "We've met over the horror, hoping Assad has reached his depths, and yet every time, he's plunged to new lows."

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