Everybody would like to minimize their time apart and if there was a sure-fire, never-fail way to do it, then all on this website would be ecstatic instead of moaning. You have various options but K3 isn't likely in your future. It's still on the books, but rarely happens any more. For the K3, the US citizen (USC) filed a form I-130 petition, followed by an I-129F when they got their receipt for the I-130. Then it was a race to see which got approved first.
I-130 win= CR1 spouse visa
I-129F win= K3 spouse visa
It used to take the I-130 forever so the I-129F would win. Then the process got so fast that the I-130 often won or they got approved at the same time. So the USCIS made a new ruling that when I-130 is approved, the other petition is administratively closed and won't go forward toward a K3. That is what happens pretty much to every case now, so K3 is an old concept.
Marry now of you wish and start the I-130 petition as an LPR. You know there is a wait for visa availability in that scenario because the numbers are limited. But once you get your citizenship, you can inform USCIS and she moves out of the line waiting for availability because there are no limits for spouses of USCs. You get started in the queue faster that way toward the CR1 visa. She remains in the UK during processing.
Or marry later, get your citizenship, and file the I-130. You start your processing at a slightly later date toward the CR1visa while she remains in the UK.
Or get your citizenship, then file the I-129F fiancé petition and she comes here, you marry, she files for adjustment of status (AOS) to get the greencard.
I think CR1 visa is best if you are ready to marry soon. Either way you go, it's going to take maybe 8 months or so and that is a very rough generalization.
There's other options people do like marry while on visa waiver and adjust status without returning to the UK. It's a bit risky and there is no appeal if it all goes pear shaped. Then you've got that overstay on the books that could result in a 3 or 10 year ban from the US. Many people pull it off, but planning to enter as a tourist with immigrant intent is considered fraud, so most do it the proper way because they feel safer that way. Depends on your risk tolerance and if she has anything that might make her inadmissable like crime, drugs, etc. People are advised not to leave the US under any circumstance if doing it that way until the greencard is in hand. So is she prepared for that, even if her best friend wants her to be a bridesmaid in the UK or somebody in her family dies?
Lots to consider, but when you choose, there will be lots of people to answer your questions here on Visa Journey.
Just a correction: the NVC administratively closes the I-129F petition if received at the same time or after they receive the I-130. The USCIS has nothing to do with the K3 being obsolete.
Jon Paul: the best option for you two depends on factors like when and where you want to be married as well as cost.
A k1 visa allows for a small amount of wedding planning time BUT you have to marry in the USA and the actual date can't be set until the visa is in hand.
It is the more expensive option.
Your fiancee (who will be your wife) cannot leave the USA without advance parole until she receives her green card.
She also cannot work for quite some time either.
It can take less time to go through
you'll be a couple after marriage
CR1 visa allows for as much wedding planning as you want and you can get married anywhere.
It's less expensive
Your fiancee (who will be your wife) can leave and enter the USA using the visa stamp as a temporary green
She can work as soon as she can get an SSN
Can take more time to go through but currently seems to be taking less
You will probably spend time apart but as she is part of a VWP country she can visit for up to 3 months at a time.
