John Swinney has been accused of putting the relationship with the US under threat after he suggested he would "consider" banning US military planes from a key Scottish airport. The First Minister said US military aircraft could be banned from using Glasgow Prestwick Airport by if it was confirmed they were involved in strikes in the Middle East. Mr Swinney said he was seeking clarity from Westminster about US planes using the Scottish Government-owned airport. The SNP leader is under pressure from the Scottish Greens who have urged the First Minister to bar American military jets from using the South Ayrshire airport. TRENDING Stories Videos Your Say The First Minister told the BBC: "We're seeking clarity from the United Kingdom Government about the purpose of American flights that are coming in and out of Prestwick, but we don't have the ability to scrutinise those flights." When pressed if he would ban the flights if it was confirmed that they were involved with the Middle East operation, Mr Swinney said: "I will consider that based on the evidence that's provided to me." Scottish Green co-leader Ross Greer said in the week leading up to the attack on Iran, there had been a "significant increase in American military activity there", adding 24 US military aircraft had landed at the airport. He noted Mr Swinney had already said the attack on Iran was "not compatible with the international rules-based system", with Mr Greer adding: "In other words it is illegal under international law." The Green MSP said: "The US is using an airport owned by the Scottish Government to wage an illegal war, killings hundreds, if not thousands of innocent people. "But at the moment Scotland’s First Minister is sitting on his hands. "Why won’t the First Minister kick Trump’s troops out of Prestwick Airport immediately?" Mr Swinney stressed again that he could "not see how the intervention by the United States and Israel is compatible with an international rules-based system." LATEST DEVELOPMENTS Iran apologises for Middle East strikes after Donald Trump warned of 'biggest bombing campaign' yet US bombers to arrive in Britain within days ahead of critical Iran mission Protesters burn Israeli flag at pro-Ayatollah vigil in Birmingham while chanting 'death to the IDF' In the interchange at this week's First Minister's Questions, Mr Swinney stressed again that he could "not see how the intervention by the United States and Israel is compatible with an international rules-based system." He added his Government is "in the process of establishing clarity around the use by the American air force of Prestwick Airport", and he vowed that when there is "more to say on that, we will share that with Parliament." However he made clear he is "in no way shape or form a supporter of what has happened in the course of the last few days”. Mr Swinney said: "Let me reiterate I believe the intervention by Israel and by the United States is incompatible with the international rules-based system. That has been the position of my Government and will continue to be so." The Ministry of Defence confirmed this morning the US has started using British bases for "specific defensive operations" to prevent Iran firing missiles into the region. A Merlin helicopter is also being sent to the region to help with surveillance from the air and RAF Typhoon and F-35 jets are continuing air operations over Jordan, Qatar and Cyprus. Protesters gathered in London today, calling for the end of US and Israeli strikes on Iran, marching from Millbank, near Westminster to the US Embassy in Nine Elms. Some demonstrators spoke through a microphone on a stage set up outside the embassy, chanting: "From Iran to Palestine, bombing children is a crime." Following reports that an aircraft carrier was being prepared in response to the Middle East crisis, GB News understands that no decisions have been taken to deploy HMS Prince of Wales, and the work being undertaken does not preclude it undertaking other planned missions. A Ministry of Defence spokesman said: "We have been bolstering our UK military presence in the Middle East since January, and we have already deployed capabilities to protect British people and our allies in the region, including Typhoons, F-35 jets, air defence systems and an extra 400 personnel into Cyprus. "Since the strikes began, we’ve had British jets in the sky shooting down drowns and have sent additional assets to the region to further reinforce our air defences, including more Typhoons and Wildcat helicopters with drone busting missiles. "HMS Prince of Wales has always been on very high readiness and we are increasing the preparedness of the carrier, reducing the time it would take to set sail for any deployment." Our Standards: The GB News Editorial Charter