The Republican leader in the House of Representatives has said that Congress would not “write a blank cheque to Ukraine” if his party wins next month’s midterm elections, stoking fears in Kyiv that the flow of military equipment could be cut off.

However, another senior Republican said that he thought that the Ukrainians should “get what they need”, including longer-range missiles than those the Biden administration has so far been prepared to supply. Analysts say the mixed messages reflect an internal debate between traditional national security conservatives and the Trumpist wing of the party, where pro-Russian sentiment is much stronger.

Kevin McCarthy, the House minority leader, told the Punchbowl News website on Tuesday: “I think people are going to be sitting in a recession and they’re not going to write a blank cheque to Ukraine.”

“They just won’t do it,” McCarthy added. “It’s not a free blank cheque. And then there’s the things [the Biden administration] is not doing domestically: not doing the border and people begin to weigh that. Ukraine is important, but at the same time it can’t be the only thing they do, and it can’t be a blank cheque.”

A few hours later, however, the ranking Republican on the House foreign affairs committee, Michael McCaul, who is likely to run the committee in the event of a Republican win in November, argued that arms supplies to Ukraine should be stepped up.

“We’ve got to give them what they need. When we give them what they need, they win,” McCaul said on the Bloomberg television channel. In particular he referred to the Army Tactical Missile System (ATACMS), which has a longer range than the missiles the administration is currently providing.

The Biden administration has withheld ATACMS so far for fear that if they were fired into Russian territory it might lead to a sharp escalation that could end up entangling Nato. McCaul argued that the missiles would be useful for striking Russian missile and drone launching sites in Crimea, adding: “Last time I checked, Crimea is occupied illegally by Russians.”

McCaul did add a caveat on US spending on Ukrainian aid, however.

“I think you’ll see if we get the majority, more oversight and accountability in terms of funding and where the money’s going, and I think the American taxpayer deserves that,” he said.

Elisabeth Braw, a fellow at the American Enterprise Institute, said the difference in tone reflected internal foreign policy tensions.

“This is a good illustration of the two factions within the Republican party,” Braw said. “You’ve got the Trumpian side and then the more traditional Republican side, and on the Ukrainian issue, this has been played out in a very clear fashion.”

In another example of the internal friction, the Twitter account of the Conservative Political Action Committee (CPAC), which is close to the pro-Russian Hungarian leader, Viktor Orbán, put up a post at the end of September asking when Biden and the Democrats would end the “gift-giving to Ukraine”. The tweet was accompanied by a graphic that mentioned the “official annexation” by Russia of four Ukrainian regions, which it described as “Ukrainian occupied”.

The tweet was taken down a few hours later and replaced with another describing the original as an “unapproved” statement and one that “belittled the plight of the innocent Ukrainian people”.

Donald Trump has a long record of admiration for Vladimir Putin and has suggested that the Ukrainians make a deal with him, highlighting the Kremlin’s nuclear threats.

“We must demand the immediate negotiation of a peaceful end to the war in Ukraine or we will end up in world war three,” the former president said at a rally this month. “There will be nothing left of our planet – all because stupid people didn’t have a clue … They don’t understand the power of nuclear.”

Far-right Trumpist Republicans like Marjorie Taylor Greene have echoed Moscow talking points, suggesting that the Ukrainian government “only exists because the Obama state department helped to overthrow the previous regime”.

Victoria Coates, Trump’s former deputy national security adviser, said that such views were held by only a minority in the party.

“There is broad bipartisan support for assistance to Ukraine among the American people, so there will be broad bipartisan support in Congress,” Coates said. But she added: “It has just seemed to many of us on the Republican side that the administration is throwing money at the situation … I think we desperately need congressional oversight of additional funds that are appropriated for this purpose.”

Coates, now senior research fellow at the Heritage Foundation, argued that the negotiations that Trump was calling for would not mean putting pressure on Ukraine to make territorial concessions.

She said: “I think we have the advantage right now and he would, I assume, agree with that, and that we should, if we do enter into a negotiation, press hard for terms that are favourable to Kyiv and Washington.”