MADRID (Reuters) - U.S. House of Representatives Speaker Nancy Pelosi took her duel with Donald Trump to a climate summit on Monday, pledging that Congress would urgently tackle global warming despite the president’s opposition to an international pact.

“By coming here we want to say to everyone we are still in, the United States is still in,” Pelosi told reporters on the first day of the two-week United Nations climate talks in Spain.

Many governments and environmental groups are aghast at Trump’s move last month to begin formal proceedings to yank the United States, one of the world’s biggest polluters, from the 2015 Paris Agreement to avert catastrophic temperature rises.

Trump says complying with the accord would hurt the U.S. economy, restricting domestic producers while other big polluters such as China increase emissions.

But Pelosi, who is also leading the Democrats’ push to impeach the Republican president, sought to reassure allies.

“Our delegation is here to send a message that Congress’s commitment to take action on the climate crisis is iron clad,” she said, flanked by Democratic Congressional representatives.

Pelosi said her decision to visit Madrid during impeachment proceedings showed Democrats were committed to tackling the “existential threat to humanity” from the climate crisis.

“We aren’t here to talk about impeachment of the president of the United States,” Pelosi said in response to a question.

“We’re here to talk positively about our agenda to save the planet for future generations.”

The United States rallied support for the Paris Agreement under the administration of former U.S. President Barack Obama. Democrats want to reassure the rest of the world they will once again throw their country’s weight behind the deal if they regain power at elections in November 2020.

Florida Congresswoman Kathy Castor, chair of the House select committee on climate, said the committee will put forward recommendations in March for a comprehensive climate change bill to bring U.S. emissions to net zero by 2050.

But achieving consensus around future U.S. legislation will be a challenge, with campaigners pushing lawmakers and Democratic presidential candidates to pursue a sweeping Green New Deal that twins climate action with social justice.