Boris Johnson suggested the chances of London Heathrow airport building a third runway anytime soon are low, as he deflected a question in the House of Commons about whether he’d live up to a pledge to try to block the building work.

The U.K. prime minister was asked if he would follow up his 2015 promise by Liberal Democrat Member of Parliament Munira Wilson, whose constituency in southwest London lies under the flight path of aircraft approaching Heathrow.

“Building a third runway is an act of environmental vandalism,” Wilson said. “Will the prime minister now prove his credentials on climate change, make good his promise of lying down in front of the bulldozers, or far more simply, just cancel the third runway?”

Johnson declined to reinforce his pledge, which he made when he was elected to represent another district affected by the proposed airport expansion. But he suggested there would be no need to take any action because of a lack of construction activity.

“I seen no bulldozers at present nor any immediate prospect of them arriving,” he replied.

Heathrow’s 16 billion-pound ($20.7 billion) expansion plan was approved by the Commons in 2018, and last year overcame a challenge by environmental groups to block it. The airport announced in December that a decision on the project’s costs by the Civil Aviation Authority had delayed the timetable for the work, which is now expected to be completed by late 2029.