BRUSSELS — British Prime Minister Theresa May tried to rally European Union leaders into a unified stance Thursday against Russia, saying the poisoning of a former spy on English soil shows that Moscow poses a long-term threat to the West.

But as Russia denied responsibility and slammed Britain’s investigation into the nerve-agent attack, some European leaders urged caution while the investigation continues.

Sergei Skripal and his daughter Yulia remain unconscious in critical but stable condition after the March 4 nerve agent attack in the English city of Salisbury, which has sparked an east-west diplomatic crisis.

Only subscribers are eligible to post comments. Please subscribe or login to participate in the conversation. Here’s why.

Use the form below to reset your password. When you've submitted your account email, we will send an email with a reset code.