Nancy Pelosi folded on Thursday and voted through a Senate version of a $4.6 billion humanitarian aid bill for the border that both the White House and the moderate wing of her party wanted - prompting fury from Alexandria Ocasio-Cortez and other left-wing Democrats.

AOC tweeted 'Hell no!' in reaction to the Speaker's reversal - which came a few hours after Pelosi accused Donald Trump of 'endangering children' and warned the president she is a 'lioness' when it comes to protecting kids.

She argued she was moving the Senate legislation ahead of her own House bill for the sake of migrant children being held at the border.

'The children come first. At the end of the day, we have to make sure that the resources needed to protect the children are available.

'Therefore, we will not engage in the same disrespectful behavior that the Senate did in ignoring our priorities. In order to get resources to the children fastest, we will reluctantly pass the Senate bill,' Pelosi wrote in a letter colleagues Thursday afternoon.

'As we pass the Senate bill, we will do so with a Battle Cry as to how we go forward to protect children in a way that truly honors their dignity and worth,' she added.

The House passed the Senate measure 305-102 later Thursday afternoon. It now goes to Trump for his signature.

He tweeted his approval for the measure from Japan, where he is at the G-20 conference, saying: 'A great job done by all!'

But Pelosi now faces fury from the left. Alexandra Ocasio-Cortez voted against the bill, and told CNN: 'We are immediately going to just saying yes to what got passed out of the Senate. 'We are a house majority and we need to act like it.'

AOC tweeted 'Hell no!' in reaction to the Speaker's reversal - which came a few hours after Pelosi accused Donald Trump of 'endangering children' and warned the president she is a 'lioness' when it comes to protecting kids.

Nancy Pelosi folded to the Senate and the White House and passed a $4.6 billion border funding bill which the left-wing of her caucus vehemently oppose

Something to smile about: Donald Trump - who had dinner in Japan with Australia's prime minister Scott Morrison - now gets to sign a bill he approves of

Not happy: Alexandria Ocasio-Cortez and the left-wing Democrats of whom she is the most prominent voice, are now in uproar at Pelosi's move. Rahida Tlaib, the Michigan congresswoman who said of Trump 'impeach the motherf***er' told CNN: 'You’re just throwing money and saying continue what you’re doing, President Trump.'

She and other left-wing Democrats, and the entire Hispanic caucus, complained about the bill giving more money for Immigration and Customs Enforcement, and said it should simply pay for 'humanitarian' resources for children at the border.

Rahida Tlaib, the Michigan congresswoman who said of Trump 'impeach the motherf***er' voiced her anger at the move.

She told CNN: 'Senate Democrats joined the leadership behind McConnell and supported something that had no safeguards, no basic human rights for these children. What are you doing? You’re just throwing money and saying continue what you’re doing, President Trump.'

Democrats pushed the blame on to Senate Democratic leader Charles Schumer.

'Schumer backed us into a corner by giving away too many votes on the Senate version,' a House Democratic leadership aide told DailyMail.com.

Schumer supported the Senate legislation along with a majority of Democratic senators.

House moderates also reportedly told Pelosi they wanted a vote on a 'clean' version the Senate legislation, citing its bipartisan support. A 'clean' version means no amendments added, such as the sweeteners Pelosi put on the House version of the measure to ensure liberal support.

Hours earlier Pelosi told reporters on Capitol Hill she would fight for the House version because she fights like a 'lioness' for kids.

'I would be considered one who's not inclined to violence and in anyway of but if you start endangering children I become a lioness, you get near those cubs and it just evokes a response that is natural,' she said Thursday morning.

Pelosi announced the House would vote on the Senate bill

'And as a mother five and a grandmother of nine I just feel that way about all children,' the speaker added.

The White House laid down the gauntlet during Pelosi's press conference, putting out a statement urging the House to pass the Senate version of border aid bill that contains provisions more preferable to the administration.

'The only ones delaying help for the children are the Democrats,' said press secretary Sarah Sanders in one of her last statements.

'We have already negotiated a broadly supported bipartisan funding bill. It is time for House Democrats to pass the Senate bill and stop delaying funding to deal with this very real humanitarian crisis,' she said.

House Republicans, in a great display of theater, lined up on the House floor Thursday morning to ask the chamber take up the Senate bill for a vote.

They all gave some same version of the legislative request: 'I asked unanimous consent to take the speaker's from the speaker's table HR 341 with the Senate amendment there to and concur in the Senate amendment. This bipartisan bill passed the Senate with 84 votes and could be sent to the president's desk for his signature today.'

One by one they made a motion only to be denied by Democratic Rep. Shelia Jackson Lee of Texas, who was presiding over the chamber.

'As the chair has previously advised, the unanimous consent request cannot be entertained,' she said repeatedly to each motion.

House Democrats blamed the cave-in on Senate Democratic Leader Chuck Schumer

House Republicans line up on the chamber floor to ask Democrats take up the Senate version of a humanitarian aid bill

Pelosi, who is Catholic, said the debate over the two versions of the legislation was about 'God's children' and protecting them.

'This isn't about threats or challenges or anything, it's s only about humanity and the courage to do what is right for the children,' she said.

And she placed the blame for the impasse in negotiations on Senate Republican Leader Mitch McConnell.

'The president was seeing well disposed to some of what we were posing. And here's the thing to be afraid of. I don't see that thing coming from the administration. I see that coming from Mitch McConnell, and I just don't know why,' she said.

'We respected the fact that the Senate has passed their bill because they should respect the fact that we've passed ours. So if this is how we see things for the future - cooperation is a two way street. And when you're talking about the children, this is a very big priority for us so we'll continue our conversation about threats and without predictions,' she added.

Pelosi, who spoke with President Trump about the legislation before he left for the G20 summit in Japan, said she would be speaking to Vice President Mike Pence later.

At the time she did not rule out the House passing the Senate version of the bill but said negotiations must continue.

'We are looking forward to having further conversations on this matter. One step at the time,' she said.

The photo of Oscar Alberto Martinez Ramierz, who drowned with his daughter Valeria, went viral and sparked a sense of urgency in passing aid for the border

Oscar Alberto Martinez Ramierz with daughter Valeria; the two died trying to cross the Rio Grande to illegally enter the United State

The speaker choked up when asked her reaction to the photo of Oscar Alberto Martinez Ramierz and daughter Valeria, the Salvadoran immigrants who drowned when trying to cross the Rio Grande.

'Can you just imagine the father put the little girl back on the shore to go back and get the mother and the little girl wanted to be with her father. She got back. He couldn't save her and he couldn't save himself. This is such a tragedy,' she said.

'I can just image how that would happen and I think it's just such a shame that would be the face of America around the world,' Pelosi added.

McConnell, in the meantime, had asked the House to pass the Senate version of the bill.

'For weeks, we have heard our House Democratic colleagues speak a lot about the poor conditions, the overstretched facilities, the insufficient supplies. Today, our bill gives them the chance to actually do something about it,' he said Thursday on the Senate floor.

Senate Republican Leader Mitch McConnell is pushing the House to pass his chamber's version of aid for the border

On Wednesday the Republican-controlled Senate and Democratic-controlled House had passed separate measures to offer humanitarian funding to immigrants crossing the border.

The White House had been clear it preferred the Senate's legislation but Pelosi tacked on several riders to the House version in order to ensure the votes of the more liberal members of her party, which she needed to get the measure passed.

Congress plans to leave Washington D.C. on Thursday for an 11-day July 4 recess, and pressure is intense to wrap up the legislation before then.

The funding is needed to prevent the humanitarian crisis on the border from getting worse.

Both House and Senate measures contain more than $1 billion to shelter and feed migrants detained by the border patrol and almost $3 billion to care for unaccompanied migrant children who are turned over the Department of Health and Human Services.

The Senate measure is not as strict in setting conditions on the delivery of funding. It also has provision opposed by House Democrats for the Pentagon and to ease a payroll pinch at Immigration and Customs Enforcement.

Neither bill would allow the Trump administration to shift any of the funds to build the president's border wall.

The White House has threatened to veto the House bill and is only reluctantly backing the Senate measure, which has large bipartisan support in the upper chamber.