Speaking to reporters in Berlin, Oudkirk said the project could sanctioned under a bill passed in August 2017.
The US opposes the project because it will increase Europe's reliance on Russian Federation for gas supplies.
According to sources in the White house and Brussels, trump announced his position on the pipeline at talks with Chancellor Angela Merkel in April.
The US threats to Nord Stream 2, which has split eastern and western European Union states, could impact companies in Austria, France, Germany and the Netherlands.
"Does he agree that there appears to be no economic justification for this, but it is instead a political project created to increase European dependence on Russian gas and to weaken Ukraine and will he press that point on our allies, particularly Germany and Denmark?"
"Germany hooks up a pipeline into Russian Federation, where Germany is going to be paying billions of dollars for energy into Russian Federation".
Trump told Chancellor Angela Merkel last month that Berlin should drop support for the pipeline linking Russian Federation and Germany if it wants to avoid a trans-Atlantic trade war, according to a report by The Wall Street Journal, which cited U.S., German and European officials.
Oudkirk said Washington's objections included past Russian moves to turn off gas supplies to Ukraine and other countries, adding that it would perpetuate "vulnerabilities" in Russian-European ties for another 30 to 40 years.
But he accused Washington of wanting to block the pipeline, built by Russia's state-controlled energy giant Gazprom and a consortium of European energy companies, in order to boost its own shale gas exports.
"The new project would permit new technologies to be placed along the pipeline route, and that is a threat", she said.
US President Donald Trump plans to promote US liquefied natural gas (LNG) exports at a meeting next Thursday (6 July) in Warsaw with a dozen leaders from Central and Eastern Europe, a region heavily reliant on Russian supplies.