WASHINGTON Senate Republicans on Wednesday blocked debate on additional U.S. support for Ukraine because President Joe Biden s proposed emergency spending bill does not include major changes to U.S. immigration or asylum laws.

The procedural vote in the upper chamber was the latest failed effort in Congress to replenish arms and munitions for Kyiv in the face of continued Russian aggression. U.S. aid is expected to run dry by the end of the year, putting at risk not only the sovereignty of Ukraine but, some fear, the rest of Europe.

Republicans are demanding sharp immigration restrictions that are meant to stem the influx of migrants at the U.S.-Mexico border, tying the matter of support for a key U.S. ally to a controversial issue that has bedeviled lawmakers in Congress for decades.

The GOP push for tighter border policy in exchange for support for Ukraine includes Senate Minority Leader Mitch McConnell (R-Ky.), a vocal advocate for standing up to Russian President Vladimir Putin and other autocrats around the world, since not doing so would cost the U.S. even more in the long run.

Ive spent months highlighting the undeniable links between the threats we face in Europe, in the Middle East, and in the Indo-Pacific, McConnell said in a speech on Wednesday. But Democratic leadership appears to be telling us today that theyre willing to risk each of these urgent priorities to avoid fixing our own borders right here at home.

Democrats , meanwhile, accused Republicans of being unwilling to compromise over border policy, and of making extreme demands that would punish people legitimately seeking asylum and humanitarian assistance in the U.S. and would pave the road for further draconian immigration measures should Donald Trump wind up in the White House again.

Lots of Democrats are going to vote against any changes we make to the border because theyre worried about what a future President Trump might do with the changes weve made, Sen. Chris Murphy (D-Conn.), a key Democratic negotiator over border issues, told reporters on Wednesday.

A group of 11 Senate progressives issued a joint statement last week that warned about potential changes to U.S. asylum laws, saying they would potentially deny lifesaving humanitarian protection for vulnerable people, including children, and fail to deliver any meaningful improvement to the situation at the border.

Bidens $110 billion emergency spending request to Congress already includes funding to boost enforcement on the border, as well as additional billions of dollars in aid to Israel and Taiwan.

Its unclear what the path ahead is for Ukraine aid in Congress, but Biden suggested on Wednesday that he is open to making some sort of compromise on immigration policy with Republican lawmakers.

Ive asked for billions of dollars for more border agents, more immigration judges, more asylum officers, Biden said at the White House. Republicans have to decide if they want a political issue or if they want a solution at the border. Do they really want a solution?

I am willing to make significant compromises on the border. We need to fix the broken border system, he added, echoing Republican complaints about the immigration system.