The clause allows for unilateral action if the Northern Ireland Protocol, which governs post-Brexit trade with the EU, is deemed to be having a negative impact.
Speaking in Brussels ahead of a meeting with European Commission Vice-President Maros Sefcovic, Frost said that Article 16 remains "very much on the table."
Difficulties in sending some goods to British-run Northern Ireland have prompted London to repeatedly call for widespread changes to the protocol and threaten to trigger safeguard measures in the deal if the EU fails to agree to an overhaul.
The European Commission last month offered Britain a package of measures it said could halve customs paperwork, cut checks on meat, dairy and other British food products by 80% and ensure the undisturbed flow of medicines.
London has said the proposals do not go far enough.