( CNN) The top Democrat in Congress on Friday called for President Donald Trump to cancel his upcoming summit with Russian President Vladimir Putin after the Justice Department announced indictments against 12 Russian nationals, that accused them of engaging in a “sustained effort” to hack Democrats' emails and computer networks.

The top Democrat in the House, Rep. Nancy Pelosi of California, tweeted, ” @realDonaldTrump must immediately cancel his meeting with Putin.”

Pelosi had said in an earlier statement, “The stakes for the upcoming Trump-Putin meeting could not be higher. President Trump must demand and secure a real, concrete and comprehensive agreement that the Russians will cease their ongoing assaults on our democracy. Failing to stand up to Putin would constitute a profound betrayal of the Constitution and our democracy.”