Foreign Affairs Minister Mélanie Joly says Ottawa prohibits any Canadian-made weapons from reaching the Gaza Strip.
Her comments come weeks after the U.S. announced plans to send Quebec-made ammunition to Israel.
In March, the Liberals joined the NDP to pass a motion to stop authorizing arms exports to Israel, though permits approved in the prior months are still active.
Global Affairs Canada previously declined to say whether the proposed American purchase violates that agreement.
Joly now says Ottawa's policy is that Canadian-made arms and components cannot be used in the Gaza Strip, regardless of how they are sent to Israel.
Ottawa stopped approving new arms permits for Israel in January, and Joly says she has also had 30 existing permits suspended.
The company named in the proposed U.S. sale, the Quebec branch of General Dynamics, has referred questions to the U.S. military.
Last week, major civil-society groups called on Ottawa to expand restrictions on military exports on Israel to a total ban.
The request cited possible violations of international humanitarian law in Israel's bombardment of the Gaza Strip following an attack by Hamas last fall.
