It was not his place to get ahead of the Cabinet process when it came to honouring National's promise to fund specific cancer treatments, he told Checkpoint.
It remains unclear how exactly the treatments will be paid for and when they will arrive, with conflicting statements by various ministers since the Budget.
Seymour said there were options that were being worked through as quickly as possible.
However, during Parliament's inaugural scrutiny week, Health Minister Shane Reti has doubled down on the need to fund the 13 cancer medications.
That's despite failing to deliver in the Budget, prompting a public outcry.
Medical experts, including oncologist Chris Jackson, have also raised concerns about some drugs on the list being outdated and Pharmac's independence and bargaining power being undermined by politicians.
Seymour told Checkpoint: "We're part of a coalition government and we are committed to doing the best we can in every case to honour the commitments that our three constituent parties have made to voters".
Asked if Pharmac had been undermined by National's move, he responded: "Ultimately, it's Pharmac that makes funding decisions to choose the best treatments that we can afford within a fixed budget," he said.
"In defence of the the National Party commitment, all three parties have signed up to that. It was never a politician. This came from the Cancer Control Agency which was set up by the government to investigate matters around cancer.
"They said, look, in terms of cancer, these are the ones that are available in Australia, are not available here and therefore these are the ones we think should be prioritised."
If he committed to funding the 13 specific drugs, it would be getting ahead of the process that Cabinet makes.
"I think what we need right now is just a really disciplined and thoughtful approach that will get the best possible outcome for the patients who I think have been forgotten amongst all the politics here."
He recognised the purchase of the drugs was critical for patients who had cancer.
"There's probably more politics in this than there needs to be so far."
However, the proper process was to take a paper to Cabinet outlining the options.
These included: Directing Pharmac to fund specific drugs, give it more money or set up "an alternative pathway" to buy the drugs as the previous government did to buy Covid-19 vaccines.
"Out of respect to my Cabinet colleagues, I'm not going to start speculating what that decision might be," he said.
"I think it's fair to say that we're moving through them [the options] as quickly as possible to make sure we get good value for every patient and also honour the commitments that parties, in this case National, has made for the New Zealand people. "
He said in response to questions of a possible announcement next week, "if that was the case, it wouldn't be up to me to pre-announce it".
"If there was to be an announcement next week, then that'll be decided by Cabinet and signalled the way that things should be done, where everyone's voice within the government is heard and the decision's one we've signed up to."
RNZ
