Britain will study the "options" with its allies if President Bashar al-Assad again uses chemical weapons against his people in Syria, but as yet there is nothing planned, Johnson also said on Sunday.
Mrs May said the action would also send a "clear signal" to anyone else who believed they could use chemical weapons "with impunity".
Meanwhile global chemical weapons watchdog OPCW inspectors arrived in Syria Saturday and were due to try to reach the site of a suspected poison attack in the Syrian town of Douma in eastern Ghouta.
"The reason they're not doing it is they are frightened they'll lose the vote".
Theresa May will give a statement to parliament on Monday, setting out her case for military action.
Asked if Russian Federation or the U.S. posed the greatest threat to world peace, Ms Abbott said: "It's clear that at this point Russian Federation, its role in Syria, what we believe, beyond reasonable doubt, is its role in the poison gas attacks in Salisbury, is a greater threat to world peace than the United States".
The diplomatic discussions are starting to feel like part of a waiting game.
Evidence is still being gathered, but United States officials are understood to have results from blood and urine samples that indicate chlorine and a nerve agent were used in the Syrian town of Douma.
He said chlorine has been used by "a number of parties in the conflict" in Syria as a weapon.
He has accused her of allowing the timing of the intervention to be dictated by US President Donald Trump and French President Emmanuel Macron, and has questioned the legality of the raids.
"Cabinet agreed the prime minister should continue to work with allies in the United States and France to coordinate an worldwide response", the statement added.
The UK's National Security Adviser, Sir Mark Sedwill, also set out further information about why the Government believed Russian Federation was responsible, saying only it had the "technical means, operational experience and the motive to carry out the attack". "Could be very soon or not so soon at all", he added.
The scheme would involve the next Labour government providing funds to local authorities who introduce bus franchising, or who take their local bus services back under public control.
But British involvement in further military intervention is controversial at home, in a country still haunted by its role in the US-led invasion of Iraq.
Her office said that she had talked with Mr Trump by telephone on Thursday evening to discuss Syria.
He said: 'Parliament must be consulted on this.