Overseas tonight, British prime minister Theresa may taking on Vladimir Putin, holding Russia accountable for that nerve agent attack. The prime minister today expeopling 23 Russian dip low malts similar to what former president Obama did here after that meddling in the election. And eye-opening words tonight from U.S. Ambassador to the U.N. Nikki Haley, who today warned that if immediate action is not taken against Russia, chemical weapons could be used here in New York City. ABC's chief foreign correspondent Terry Moran in London tonight. Reporter: Speaking to a hushed parliament, prime minister Theresa may spoke with an icy fury. We will not tolerate the threat to life of British people and others on British soil from the Russian government. Reporter: British investigators say a military-grade nerve agent developed by Russia was used in the attack on a former Russian spy and his daughter, a conclusion now backed by the U.S. Intelligence community. In retaliation, may said Britain will expel 23 Russian diplomats, giving them one leek to leave. Suspend all high-level contacts with Russia. Take unspecified clandestine measures. And she added the royal family will boycott the soccer world cup in Russia this summer. The expulsion of diplomats, the biggest here since the cold war, and echoing president Obama's kicking out 35 Russian diplomats from the U.S. In retaliation for Russian meddling in the 2016 election. Later, dramatic scenes at the U.N. Security council. Russia in the dock. Britain asking the world to stand with them. And U.S. Ambassador Nikki Haley backing the Brits, urging the world to act. If we don't take immediate, concrete measures to address this now, Salisbury will not be the last place we see chemical weapons used. They could be used here in new York. Or in cities of any country that sits on this council. And Terry Moran joins us live tonight. Very strong words there from Nikki Haley. Senior intelligence officials telling ABC that there is now daylight between U.S. And British assessments on this, that the Russians are guilty here. What is the president, the white house saying tonight? Reporter: Well, David, the president told reporters yesterday, as soon as we get the facts straight, if we agree with them, we will condemn Russia or whoever. The facts are in, intelligence agencies, as you say, agree. Tonight, a strong statement from the white house, saying the United States stands in solidarity with its closest ally, the United Kingdom, and is working together with our allies and partners to ensure this kind oaf abhorrent attack does not happen again. David? That statement from the white house a short time ago.