By Patricia Zengerle and Lesley Wroughton
WASHINGTON (Reuters) - U.S. lawmakers on Thursday kept up their push for the Trump administration to push back harder against Russia's "nefarious activities," even as top economic officials pledged to take a hard line on Moscow's election meddling and the poisoning of its own citizens in Britain.
Assistant Secretary of State Manisha Singh reiterated to a congressional hearing that Washington would adhere to its August pledge to impose "very severe" sanctions on Russia if it does not meet a November deadline to comply with international chemical weapons law.
"We are looking at this November deadline as absolutely, we plan to impose a very severe second round of sanctions under the (chemical and biological weapons law)," Singh told the House of Representatives Foreign Affairs Committee.
Washington said on Aug. 8 that it would impose sanctions on Russia after it determined that Moscow had used a nerve agent against a former Russian agent and his daughter in Britain.
However, Singh noted Russia would not be subject to sanctions if it meets conditions including allowing inspections and providing a "verifiable" assurance that they will not use nerve agents against their own people again.
"They have not done so, so far," she said.
The Russian ruble firmed to a one-week high against the dollar on Thursday, but its gains narrowed after Singh's remarks. The currency was last at 68.49 against the dollar.
The House hearing was the latest in a series, as lawmakers, including his fellow Republicans, kept up pressure on President Donald Trump to push back harder against Russian meddling in U.S. elections, aggression in Ukraine and involvement in the civil war in Syria.
"We cannot expect (Russian President) Vladimir Putin and his corrupt associates to change their behavior in Syria, Ukraine or anywhere else until we prove we will hold them to account," said Representative Ed Royce, the committee's chairman.
Royce also called for "secondary" sanctions targeting those who do significant business with Russian businesses or government entities subject to direct sanctions.
The committee's ranking Democrat, Representative Eliot Engel, said Congress could be doing more. Lawmakers from both parties have introduced at least eight sanctions bills in recent months.
Singh said that Trump administration sanctions have imposed substantial costs on Russia and deter "nefarious activities." She estimated they have cost the Russian government "tens of billions of dollars."
Trump signed an executive order on Wednesday to strengthen election security, just eight weeks before Nov. 6 U.S. congressional polls, by slapping sanctions on foreign countries or people who try to interfere in U.S. votes.
(Editing by Bernadette Baum and James Dalgleish)