Senate Minority Leader Charles E. Schumer (D-N.Y.) speaks with reporters at the Capitol on Feb. 15. (Mario Tama/Getty Images)

Senate Minority Leader Charles E. Schumer (D-N.Y.) is warning that President Trump needs to release his personal tax returns if he hopes to achieve comprehensive tax reform in the coming months.

“It’s going to make tax reform much harder” if Trump doesn’t release his returns, Schumer told reporters Tuesday. Anytime the president proposes something on tax reform, “the average American is going to say, ‘Oh, he’s not doing that because it’s good for me, he’s doing it because it’s good for him.’ So for his own good, he ought to make them public. And the big mystery is why he hasn’t.”

“I think he just has an obligation to come clean. When you clean up the swamp, it’s not keeping things secret and applies to yourself,” Schumer added.

Trump paid $38 million in federal income tax in 2005 on more than $150 million, for an effective rate of 25 percent, and reported a $105 million write-down, according to a copy of his federal tax return revealed last month.

The revelation provides the most recent glimpse at Trump’s income. Last fall, the New York Times reported that Trump reported a massive $916 million loss in 1995, which enabled him to avoid paying income taxes for decades.

During the 2016 presidential campaign, Trump’s tax returns were a frequent subject of conversation, and opponents in both parties called on him to release them. Ultimately, Trump was the first presidential candidate in decades to win without making his tax returns public.

There is no legal obligation for a president to release his tax returns, and like any other citizen, they can opt to keep them private. But presidents dating back to the 1970s have released at least partial tax information in a show of transparency for voters.

Schumer said that part of the reason Democrats are eager to see Trump’s returns is to determine whether Trump or his family’s business empire have any conflicts of interest with the federal government or foreign powers.

“When China just released those 38 approvals for him a month ago, a natural question to ask is are they doing that because they’re trying to win policy points related to American workers and the American people? No one knows the answer,” he said.

Schumer made his comments in a conference call with reporters held officially to criticize Trump’s refusal so far to declare China a currency manipulator. The White House is days away from deciding whether to follow through on Trump’s campaign pledge to declare China as such — a move that could lead to new U.S. tariffs if China doesn’t change its practices.

In a tweet Tuesday morning, Trump said he told Chinese President Xi Jinping “that a trade deal with the U.S. will be far better for them if they solve the North Korean problem!”

Asked to respond, Schumer agreed that China’s currency manipulation and the current troubles in North Korea are linked “but in the opposite way of the president.”

“The Chinese have done nothing on North Korea, and I don’t think they will unless they think America is tough. The tougher we are on trade, the more likely China is going to think we’re tough on North Korea,” Schumer said.

The Senate leader also revealed that he had his first one-on-one phone call with Trump last Thursday — after U.S. military airstrikes against Syria began. Aides said Schumer was first informed of the strikes by Vice President Pence and spoke with Trump later. Schumer said that during the call he urged Trump to “be really tough” in his meetings with President Xi, but the senator and his aides declined to say what else was discussed.

Making his most expansive comments yet on the airstrikes against Syria, Schumer said there should be a “defined strategy” from the Trump administration on how to proceed.

“I for one am really, really wary and worried about getting committed to another land war,” he said, adding that “I think Congress would be opposed to that. I think he’d need Congress’s approval to do that. … I would tell him my view, and that of most of my caucus, is very, very dubious of a kind of large-scale military action we saw in Iraq. And dubious of military action generally.”

Schumer said Democrats generally oppose further military action because “we believe that our big focus has to be at home. We have to rebuild our country, our infrastructure, jobs.”