Kirk, a Republican, is the co-author along with Democratic Senator Robert Menendez of a proposal to penalize foreign financial institutions that do business with Iran’s central bank, the main conduit for its oil revenues…

Kirk said on Tuesday that the administration had written to some lawmakers’ offices and “proposed what they describe as technical fixes” to the Kirk-Menendez amendment.

But Kirk complained: “They are not technical fixes at all. They are meant to undermine the amendment.” He and Menendez have written to fellow lawmakers as well, urging them to “stick with” the Senate-passed proposal, Kirk said at an event on Iran’s nuclear program, sponsored by the conservative American Enterprise Institute think tank…

The administration also sought to “water down the penalties” on foreign banks that do business with Iran’s central bank, the Senate aide said. The administration favored imposing “strict conditions” on such foreign banks, rather than the all-out cutoff from the U.S. financial system that is in the Kirk-Menendez amendment.