"There's not any sort of option where a political solution is going to happen with Assad at the head of the regime", Haley said.
"It is in the vital national security interest of the United States to prevent and deter the spread and use of deadly chemical weapons", Trump said in announcing the attack.
An arm of Lebanese militant group Hezbollah issued a statement it claimed was on behalf of Russia, Iran and its allies, vowing to "reply with force" to any future aggression "in a variety of ways".
Eighty-six people including at least 27 children died in Khan Sheikhun in an attack the United States has blamed on Syrian President Bashar al-Assad.
Top diplomats from the seven major advanced economies are in Italy for their annual two-day meeting which had initially been expected to focus on intimate talks with new US Secretary of State Rex Tillerson about hotspots like Libya, Iran and Ukraine.
Mr Johnson has warned the U.S. could launch further airstrikes on Syria following its bombing of the Shayrat airfield near the city of Homs. Press Secretary Sean Spicer said President Donald Trump would not "telegraph his next move". "We can not miss this moment".
Russian President Vladimir Putin shakes hands with Iranian President Hassan Rouhani at the Kremlin in March.
Pre-Order of iPhone 8 Starts September, Shipment Expected Before December Holidays
The edge-to-edge display will allow Apple to keep the physical size of the device down, while increasing the size of the display. The phone features glass panels on the front and rear of the device, a curved borderless OLED display, and no Home button.
The question of Russian complicity in the attack also came up in an earlier interview on "This Week" Sunday with Secretary of State Rex Tillerson.
Some European diplomats believe USA policy is unclear because of its twin ambitions of wanting Syrian regime change and defeating Islamic State.
Washington D.C. (USA), Apr. 10 (ANI): U.S. President Donald Trump is discussing with members of his administration the possibility of introducing sanctions against Russian Federation and Iran for supporting the Syrian Government.U.S. Ambassador to the United Nations Nikki Haley said on Sunday.
Those comments came a day after the USA ambassador to the United Nations said there was no way to stabilise Syria with Mr Assad as president.
The US and United Kingdom blame Russian Federation for being complicit in the deaths of Syrian civilians in last week's chemical attack.
Britain's Johnson cancelled a scheduled visit to Moscow Monday, saying his priority was now "to continue contact with the USA and others" ahead of Tillerson's Russian trip.
Russian state media reported that a frigate, the Admiral Grigorovich, would call at a logistics base at Tartus, Syria.