At the height of the showdown with Russia over Syria, U.S. President Donald Trump once again took to Twitter with confusing messages on Thursday, saying the anticipated attack targeting the Assad regime could happen "very soon, or not so soon at all."

"Never said when an attack on Syria would take place. Could be very soon or not so soon at all! In any event, the United States, under my Administration, has done a great job of ridding the region of ISIS. Where is our 'Thank you America?" Trump wrote.

Trump's tweet came a day after he vowed to strike the regime with a provocative tweet mocking Russia's recent warning on responding to any attack targeting the regime, declaring that missiles "will be coming" and blasting Moscow for standing by Bashar Assad, the usual suspect of the alleged chemical attack in Syria's Douma.

"Russia vows to shoot down any and all missiles fired at Syria. Get ready Russia, because they will be coming, nice and new and 'smart!' You shouldn't be partners with a Gas Killing Animal who kills his people and enjoys it!" Trump wrote in a post on Twitter Wednesday.

Meanwhile, French President Emmanuel Macron also announced Thursday that France would make a decision on whether to strike Syria "when the time comes."

"We have proof that... chemical weapons were used, at least chlorine, and that they were used by the regime of Bashar al-Assad," Macron said, adding that he would not allow an escalation of the situation across the region.

France, the United Kingdom and Saudi Arabia previously voiced support for a possible military operation in Syria, backing Trump's rhetoric.

Following Macron's announcement, Chancellor Angela Merkel said Germany won't participate in possible military action in Syria, but supports sending a message that the use of chemical weapons is unacceptable.

Merkel stressed the importance of a united position in the face of a suspected chemical weapons attack that the West is blaming on Assad forces. She said she spoke Thursday with Macron.

Merkel said in Berlin: "Germany will not take part in possible military action — I want to make clear again that there are no decisions — but we see, and support this, that everything is being done to send a signal that this use of chemical weapons is not acceptable."