Washington (CNN) President Donald Trump's nominee to be the next US ambassador to the United Nations hit headwinds Wednesday as senators questioned the impact of her family's coal fortune on her ability to work on climate issues at the world body.

Kelly Craft, the current US ambassador to Canada, acknowledged during a Senate Foreign Relations committee hearing that fossil fuels contribute to climate change and said she would recuse herself from any UN discussions on coal.

But as senators raised the question again and again, Craft hedged on the degree to which fossil fuels drive climate change, which the UN described in November as an "existential crisis." For at least one senator, Craft's nuanced stance wasn't good enough.

"At a time when climate chaos is the greatest global challenge we face, it's incredibly disturbing that President Trump has nominated a UN Ambassador with deep personal ties to and a financial stake in the coal industry," Democratic Sen. Jeff Merkley of Oregon said in a statement after the hearing, announcing his opposition to Craft's nomination.

Political connections

Craft will be replacing former ambassador Nikki Haley , who resigned in October. The job is not expected to be the Cabinet level posting that Haley insisted upon, leaving Secretary of State Michael Pompeo and national security adviser John Bolton firmly in control of US foreign policy.

But Craft's political connections as a major Republican donor, both to Trump and lawmakers, may give her more behind-the-scenes clout with the White House and the Republican-controlled Senate than Haley wielded.

On Wednesday, Craft faced questions about her extended absences from Canada during her tenure as ambassador, as well as her stance on Saudi Arabia's human rights abuses, in particular what the UN and US intelligence agencies say was the state-sanctioned and directed killing of Washington Post journalist Jamal Khashoggi

She was queried on whether the President has the right to go to war with Iran without consulting Congress and questioned on Trump administration policies on gender and women. But senators kept circling back to the issue of climate.

Craft -- who is married to the CEO of Alliance Resource Partners, one of the largest coal producers in the US -- made a stir soon after arriving in Canada for saying that when it comes to climate change "both sides have their own results, from their studies. ... I respect both sides of the science."

'It poses real risks'

Craft tried to head off questions about the issue in her opening remarks to the committee. "I understand that some members of this committee have raised questions about where I stand on climate change," she said.

"Climate change needs to be addressed as it poses real risks to our planet. Human behavior has contributed to the changing climate, let there be no doubt," Craft said. "I will take this matter seriously, and if confirmed, I will be an advocate for all countries to do their part in addressing climate change."

She said that did not mean that the US "should imperil American jobs or our economy as a whole by assuming an outsized burden on behalf of the rest of the world." And Craft said that "where there is the issue of coal and/or fossil fuels, I will recuse myself in meetings through the UN."

"I understand that fossil fuels have played a part in climate change," Craft said later in the hearing. But when asked by Massachusetts Democratic Sen. Ed Markey whether she agrees with scientists who say that the crisis is "largely because of fossil fuels and human activity," Craft hedged.

"I acknowledge there is a vast amount of science regarding climate change and the tools and the role that humans have played in climate change," she said.

GOP fundraiser

Craft, who has been a fundraiser for Republican causes and a generous donor to the Republican Party, the Republican National Committee and Trump's 2016 election campaign, has given to several of the committee Republicans who will be voting on her nomination.

According to the Federal Election Commission, in 2016 Craft donated to Sen. Todd Young of Indiana, Sen. Ron Johnson of Wyoming and Sen. Marco Rubio of Florida. She and her husband have also held fundraisers in the past for Sen. Mitt Romney of Utah, who said Wednesday that he and Craft are "long-term friends."

Craft was introduced to the committee by Senate Majority Leader Mitch McConnell of Kentucky, who spent time on the Senate floor Wednesday morning calling for the roll back of coal industry regulations

Republicans on the committee came to Craft's defense when Democrats, led by New Jersey Sen. Robert Menendez, challenged Craft on her absences from Ottawa. Menendez noted that she was away from her post more than 300 days between October 2017 and June 2019.

Craft said that she had been traveling for the trade negotiations with Canada and Mexico. When Menendez pointed out that her absences continued well after the talks were concluded -- with Craft spending an average of 20 days a month outside Canada in the eight months since negotiations ended -- Craft said other conversations were required to iron out issues.

'No fun'

"I did not enjoy living out of a suitcase ... that was no fun," Craft said.

In a rare moment of tension between a Republican and Craft, Sen. Rand Paul of Kentucky asked Craft whether she thought the Iraq War was a mistake.

"I'm not going to second guess the administration, the Bush administration," said Craft, who was a fundraiser for President George W. Bush. "But I do acknowledge President Trump has made the statement that" the war was a mistake.

Rand told Craft that she'll face questions at the UN about "whether or not regime change in the Middle East is our business," in a reference to growing tensions with Iran. "What's important is that we show strength, we show deterrence," Craft said.

Young of Indiana asked Craft if she believed the President could declare war on Iran without congressional approval.

"I understand that when we have an imminent threat the President makes this decision," Craft said. "If not that, then I also understand and I know the importance of consulting with Congress when it comes to something as important as this decision."

Pressed by Young, she said, "I agree -- yes, that we need to be consulting with Congress."

Sen. Tim Kaine, a Virginia Democrat, pushed Craft on her stance on holding Saudi Arabia's leaders accountable for the killing of US resident and journalist Jamal Khashoggi when the US takes over presidency of the Security Council in December.

UN report released Wednesday urged that Saudi Arabia's Prince Mohammed bin Salman be investigated over Khashoggi's "deliberate, premeditated execution" of Jamal Khashoggi. The report, based on the first independent investigation into the writer's death, said Crown Prince Mohammed bin Salman should be sanctioned until he proves his innocence.

Pompeo and Trump have worked to shield Saudi Arabia and the prince from any censure.

"Can you give me a commitment that the United States with you representing it as head of the Security Council will do everything possible to make sure that the investigations called for here and the accountability that would follow upon such an investigations are actively pursued by this country," Kaine asked Craft.

"Absolutely," she said. "We will, and I will give you my word on this."

Sen. Lindsey Graham, the South Carolina Republican, described the Saudi prince as "just nuts" and then asked Craft if she thought "we are at war with radical Islam."

"In many forms, yes," Craft answered.